The Africanized Bee and Honeybee
There is only one species of honeybee in the United States, namely Apis mellifera. The Africanized bee and domestic honeybee are the same species but different subspecies. As a consequence they have very similar biologies and both are important from the standpoint of pollination. Bees are the most important insects in the world because of their pollinating capabilities. Pollination is the process where pollen (the plant equivalent of sperm) is transferred to the ovule (the plant equivalent of a mammalian egg) which, when fertilized, eventually will grow into a seed or fruit. Fruits and seeds typically cannot be formed without pollination. In plants with light fluffy pollen, this transfer normally is accomplished by wind. In plants with sticky pollen, insects, birds and a few other animals accomplish pollination. Normally these animals are attracted to the flowers of these plants by the sweet nectar they produce.
In plants that are insect-pollinated, the honeybee is by far the most important participant. The value of these pollination services by honeybees is estimated at $6-$15 billion annually in the United States. Part of the reason for this value is because honeybees are attracted to a broad range of plants for the purpose of collecting nectar and pollen. Many wild bees and other insects also visit flowers, although in many cases the range of plants that they visit is quite specific. The importance of the honeybee is magnified in the United States and other countries where modern agriculture is practiced due to how crops are produced. In many states crops normally are grown in monocultures, a practice where only one crop is grown over a large geographical area. This is an extremely efficient way of growing crops but tends to reduce the number of natural pollinators in an area where it is practiced. In monocultures, many of the natural plants of an area are removed to grow the crop. Because these plants serve as an important source of food and hibernation sites, many of the natural pollinators (wild bees, beetles, flies and butterflies) tend to disappear.
The honeybee is so important because it is a domesticated animal. At the time when insect pollination of a crop should occur, a grower frequently pays a beekeeper to bring beehives into the field for this purpose. Beekeepers make about one-half their income from pollination services. Some crops that are dependent on bees for pollination include cherries, plums, prunes, apricots, peaches, some apples and pears, avocados, many melons, curcubits and most flowers and vegetables that are grown for seed.
The following is based on the biology of the European honeybee; however, in most cases the biology of the Africanized bee is almost identical. Significant differences between the two are discussed later. The honeybee is a social insect. As is true of all social insects, there are different forms or castes within a colony, each of which performs prescribed functions. In the honeybee these castes are the workers, drones, and queen.
The male or drone bee (Figure 1) is large, robust and possesses huge compound eyes that wrap entirely around the head. Because the stinger of a bee is a modified ovipositor (egg laying apparatus), male bees (Hymenoptera, in general) cannot sting. Drone bees cannot collect nectar or pollen and perform no work duties within the colony; their sole function is to mate with the queen. With the European honeybee drones are most abundant in a beehive during the spring months when the virgin queens have their mating flights. During the summer their numbers begin to decline, and by fall the worker bees force the drones out of the hive as they no longer have a function.
Figure 1. A drone honeybee with large eyes.
Mating begins when a virgin queen leaves the hive on her nuptial flight. Once out, she flies to a drone-congregation area, which is near the hive and up to 40 to 50 feet in the air. She flies as fast as she can and typically is followed by a few dozen drones. Because the strongest and fastest drone is most likely to catch her, this is a method of selecting superior genetic material. Once successful, the drone snaps his genitalia into the queen in midair. They fall to the ground and the queen eventually rips off his genitalia. Upon returning to the hive, the queen frequently can be seen with the male’s genitalia (sometimes several) hanging from the tip of her abdomen. This is referred to as "the mating sign." The queen may mate up to 30 or 40 times on her flight, but does not mate again after she returns to the hive. Typically there is only one queen in a hive at a time. Once mated, she is capable of laying 10,000 eggs a month for 3 years. Generally, after 3 years the queen is replaced.
The worker bees (Figure 2) are sterile females and, as their name implies, perform all the work duties within a bee colony. These duties include feeding the larvae, cleaning the colony, packing the pollen, converting nectar into honey, guarding the hive, secreting wax, constructing new bee combs, and collecting pollen, nectar, water and tree sap.
The number of worker bees in a hive depends primarily on the season and or the availability of food in the field. When food (nectar and pollen) is readily available and is brought into the hive by foraging workers, the queen is stimulated to produce even more workers in order to take full advantage of the situation. When this availability drops off her egg laying is reduced and fewer workers are produced. Of course this normally follows the seasons with most nectar and pollen available in the spring and summer months. Accordingly, a large hive can have upwards of 80,000 workers in the spring months. This number gradually declines to as few as several hundred during the winter.
Figure 2. Worker bees on honeycomb.
Caste determination of adult bees depends on whether an egg is fertilized or not and the diet of the developing larvae. When the queen bee (Figure 3) is laying eggs, she has the ability to withhold sperm for egg fertilization. Unfertilized eggs eventually will develop into drones. Fertilized eggs develop either into queens or worker bees. The developing larvae of all 3 castes are fed royal jelly for the first half of their lives. A developing queen larva will be fed royal jelly for her entire developmental period. Developing worker or drone larvae are provided a diet of nectar-pollen during the second half of development. The larvae of workers (yellow arrow) and drones are raised in honeycomb cells (Figure 4). Each cell is inspected up to 200 times a day by adult worker bees making sure the larvae have adequate food. Once the pupal stage is reached, adult bees seal the cells with a wax capping (red arrow). Once the adult bee inside the capped cell emerges from the pupae, it eats its way out of the cell through the wax capping (Figure 5).
Figure 3. Queen bee surrounded by workers
Figure 4. A developing worker larva (yellow arrow) and a capped over worker pupa (orange arrow).
Figure 5. A worker bee emerging from a cell.
Royal jelly is a highly proteinaceous material that is produced by glands in the heads of worker bees. It also contains hormones that enhance the process of queen development. It is said to have ’magical powers’ and has been exploited by the cosmetic industry. Frequently it is found in face creams and other products designed to enhance beauty. Royal jelly extracts are also available for human consumption. It can be spread on toast or eaten in a variety of ways. When consumed regularly it is claimed that royal jelly increases human vitality and vigor. This material is especially popular in many Asian societies. While shopping in Chiang Mai, Thailand, the authors encountered a store that sold nothing but royal jelly products.
New queens are reared under 3 conditions, namely queenlessness, swarming and supersedure. Queenlessness occurs when a predator, careless beekeeping or disease kills a queen. Within a few minutes most of the worker bees realize they that they are queenless. A living queen bee excretes a pheromone (queen substance) which is detected by her court as they groom her. In turn this chemical is passed on to other bees in the hive during grooming. In the absence of the queen, this chemical is no longer present and the workers begin the process of raising a new queen (discussed below).
Typically, worker bees will raise several new queens simultaneously in specially constructed cells (Figure 5). This is essential to protect against the chance of a single queen dying during the rearing process. The first queen to emerge from her rearing chamber will go to the other queen cells and kill them before they emerge. If 2 adult queens emerge simultaneously usually they will fight to the death. Worker bees closely referee this battle to insure that both queens are not killed.
Figure 5. A queen cell. Image courtesy of Carl Dennis, Auburn University.
Swarming typically occurs in the spring months when large amounts of pollen and nectar are available in the field. As a result the queen is stimulated to produce many worker offspring during this period in order to collect the food. As a consequence, the hive often becomes overcrowded with food and bees and swarming soon follows. On an average European bees typically only swarm once or twice a year. A swarm is formed when a newly raised queen leaves the hive with about half of the worker bees. This swarm normally flies only a few hundred yards or less from the hive and then settles down (Figure 6). At that point, if they have not reached an adequate location for the formation of a permanent hive, worker bees will scout for a more suitable location. Once this is found, they will fly back to the swarm and lead it to the new location. Unfortunately, sometimes this new location is inside the walls of a house.
Figure 6. A small bee swarm that has settled on a branch. Image courtesy of O. Keith Dooce, University of Georgia.
Supersedure is the process of replacing an old queen with a new queen. After about 3 years of age a queen begins to lose her ability to produce eggs. At that point, worker bees recognize her inadequacies and raise new queens to supersede her. Much like swarming and queenlessness, several queens are raised but only one survives. Because the old queen poses no threat to the new queen, they do not fight but work side by side until the old queen dies of natural causes.
As previously mentioned, worker bees collect nectar, pollen, water, and tree sap. Bees have many finely branched hairs on their bodies. As the bees visit flowers, these hairs trap pollen granules. While in flight, the bees use comb-like structures on their legs to remove the pollen, which eventually is packed into balls that are placed on their hind legs. These bees enter the hive and kick the balls off into the cells of the honeycomb. Hive bees later pack the pollen into the bottom of the cells. Because pollen is high in protein, adult worker bees eat it. They, in turn, convert it into royal jelly.
Bee pollen is a product that is sometimes consumed by humans. It is readily available in most health food stores. When eaten regularly, bee pollen is claimed to give the consumer great vitality and sharpness of the mind. The authors encountered an insect vendor at one of our recent insect fairs. He was extremely happy and claimed he was sleeping much better than usual and was more keenly aware of events around him. When asked why, he explained he had discovered bee pollen. I was somewhat skeptical but slightly later events at least made me think that possibly eating pollen had some merit.
The previous summer I was in Malaysia buying some insects from a dealer. I came across a huge preserved praying. I asked the dealer how much he would sell it to me for. He indicated it was of little value since it was green and gave it to me as a gift. At the fair I had it in a box of insects that were for sale. The pollen eating dealer happened by and asked how much I wanted for the praying mantid. I told him that I really didn’t want to sell it since it was a gift. He offered me $20.00 so I sold it. A few minutes later another individual walked by with the same praying mantid that he had purchased from the pollen eater. When asked how much he paid for it to my amazement he answered $100/00. The dealer certainly was on top of his game.
The beekeeper collects pollen for sale to health food stores by placing a narrow grid of parallel bars over the entrance of the hive. The distance between any two opposing bars is just wide enough to allow a worker bee into the hive. However, because the pollen balls on the outer part of the bees’ hind legs stick out, they are knocked off as the bee passes through the bars and are collected in a tray.
Tree sap is collected to mix with wax to produce a material called propolis, or bee glue. Propolis is used to secure the hive (Figure 7). Any structures that are 1/4" or closer together are glued together with this material. If tree sap is not available, bees will collect anything of similar texture, including caulking and chewing gum. Propolis is another bee product that can be purchased in health food stores. Again, claims as to its medicinal value are extremely doubtful. These include enhancement of the immunity system and antimicrobial activity.
Figure 7. Propolis (black) or bee glue used to hold top cover to hive body.
Worker bees collect water for several purposes. If an excessive amount is brought into the hive, it is stored from day to day inside a few workers that are selected to be reservoir bees. These bees are fed excessive amounts and swell to a few times their normal size. They then hang around the hive and regurgitate water to other hive bees on command. Water is used to cool the hive. If outdoor temperatures become excessive, hive bees build small wax pools on top of the frames enclosing the honeycomb and fill these pools with water. Then a number of the bees line up on the right half of the hive entrance with their heads pointing outward and begin to fan their wings (Figure 7B). This behavior draws air into the hive and over the pools, thus cooling through water evaporation. In even higher temperatures, other bees will line up on the left half of the hive entrance with their heads pointing inward and fan their wings. This increases air circulation by drawing air out of the hive.
Figure 7B. Honeybees gathered at entrance fanning wings in order to a cool hive.
Bees collect nectar by lapping it from nectaries that occur on the stems, leaves and flowers of plants. This liquid is carried back to the hive in the bee’s stomach. Nectar is composed chiefly of sugar and water. On average, nectar is 25% table sugar and 75% water, although these numbers may vary considerably depending on the source. Table sugar, or sucrose, is a complex sugar, or disaccharide. Honey, by weight, is composed of 90% simple sugars and 10% water. Therefore, to convert nectar into honey, the bees must accomplish two processes, namely get rid of the excess water, and break down or digest the disaccharide, or sucrose, into simple sugars.
The sugar breakdown is accomplished by digestion and begins as the field bee adds digestive enzymes to the nectar carried in its stomach. When the bee returns to the hive, she regurgitates the honey and feeds it to an adult hive bee that, in turn, adds more digestive enzymes.
The water is eliminated by evaporation. The hive bee regurgitates small amounts at a time and spreads it thinly over her mouthparts, working it vigorously. She then will place small drops of the nectar-honey around the hive to dry; subsequently it is collected and put into honeycomb cells. Once in the cells, evaporation continues and, when the water content in the nectar reaches the right level of honey, the bees construct a wax capping over the cells in order to preserve it.
Honey is too high in sugar concentration to feed directly to the young and must be diluted with water in order to do so. The question arises why would bees collect nectar and convert it into honey by getting rid of excess water and then in order to feed it to the young water must be added. Of course the answer is storage and preservation. If water is removed from nectar more energy (in the form of sugar) can be stored in a given area of honeycomb. In addition since honey is so high in sugar concentration bacteria and other microbes can not live in it. Therefore the high sugar concentration is a form of preservation.
Beekeeping as a science originated in England in the eighteenth century. Bees were domesticated at that time through selective breeding. In doing so apiculturists selected characteristics desirable for bees in a temperate area (e.g. England). Subsequently, these temperate bees were shipped all over the world, including the United States and South America.
In 1956, the Brazilian government, knowing that the bees in their country possessed characteristics selected for a temperate area, decided to conduct research to attempt to crossbreed their bees with bees that had evolved in a tropical area. The hope was that hybrids would be better adapted for, and more productive in the tropics. For crossbreeding with their bees they selected bees from South Africa. Apis mellifera scutellata, or the African honey bee as it is known, is native to the tropical savanna country of eastern and southern Africa. These bees were imported into Brazil in 1956. In Africa, A. mellifera scutellata, had been known to produce up to 3 times as much honey as traditional European honey bee, which was less well-adapted to tropical regions of Brazil. Because this was a wild bee and possessed certain undesirable characteristics, the government established an experimental apiary in Sao Paulo, Brazil. In order to keep the queens and drones (the only bees capable of mating and passing genetic material) inside the experimental hives, double-queen excluders were placed over the entrance to each of the hives. These excluders allowed worker bees to come and go, but prevented the departure of the larger queens and drones.
Unfortunately, a local beekeeper noticed that the double-queen excluders were slowing down the worker bees at the entrance and removed them from the hives. Before the researchers noticed this, 26 of the African beehives swarmed and eventually mated with the temperate bees in various parts of Brazil. Their offspring and their descendents are now called the “killer bees” or Africanized honeybees. Since that time, killer bees have migrated northward through Central and South America and Mexico and reached Texas in 1992. By the spring of 1999 all of Southern California and much of Texas, New Mexico and Arizona were colonized. That is to say, most of the wild or feral hives in these states are Africanized honeybees. In California their current distribution has reached up into Tulare County and is expected to eventually reach as far north as San Francisco. Their eastward migration from Texas has been greatly retarded although there is no reason to believe that they will not eventually spread throughout most of the southern US.
Biological Differences between Africanized and European Bees
Based on superficial observations it is nearly impossible to tell the difference in appearance between Africanized and European bees (Figure 8). The Africanized bee is 10% smaller in size and weighs 30% less than European bees. Morphologically experts distinguish between the two by the use of the FABIS Test (Fast Africanized Bee Identification System). This test consists of measuring wing length, leg length and several other body parts and then comparing these measurements to standard lengths for both types of bees. DNA testing is also used to confirm identification.
Figure 8. Adult Africanized bees. Image courtesy of Jerry Payne, Auburn University.
Figure 8. European bee illustrating little or no differences in overall appearance from adult africanized bee. Image courtesy of USDA Archives.
Temperate vs. Tropical Bees
As previous discussed the European honey bees are temperate bees while Africanized honey bees are tropical and as a consequence their behaviors differ in several ways. Each has a different strategy for survival that is based on and best suited for their native climate. The European honey bee is adapted to withstand cold winters when nectar and pollen are not readily available in the field and temperatures are too cold to forage. They accomplish this by building the large colonies needed to collect and store nectar and pollen that is readily available in the spring and summer months. During winter the size of the colonies is greatly reduced, hive activity slows and there is little if any brood rearing or foraging. Survival during the winter months is accomplished by utilizing food excess that is stored during the spring and summer months. Their large colonies are typically constructed inside cavities to provide winter protection.
In tropical areas of the world nectar and pollen are almost always available and winter temperatures are not prohibitive for foraging. As a consequence Africanized bees have little need to store honey and their main energies go into honey production for reproduction. Unlike European bees they will swarm many times over the entire year. Swarming ultimately produces more hives (their strategy of life). Their nests are smaller (but much more abundant) and often formed external to cavities.
Another characteristic that is found in Africanized bees but rarely if ever observed in European bees is abscounding. This occurs when the entire colony leaves or abandons the nest in the search of a new home. In the tropics this is thought to be advantageous and possible occurs when a given area is depleted of available food in the form of nectar and pollen. Again in the tropics these materials are typically available year around. In temperate areas this behavior would be detrimental and would probably occur in the late fall when food is scarce. If a colony abscounded at that time of the year in many areas of the US it would be very difficult to find food.
There are vast differences in the behavior of each type of bee. When Africanized honeybees evolved in South Africa there was always the threat from a vast array of predators (vertebrate and invertebrate). As a consequence they developed a number of defensive behaviors aimed to avoid potential predators. First, many of the returning foragers approach the hive and fly through the entrance at a high rate of speed reducing this potential danger at this critical point. European bees land on the landing board of a hive and slowly walk in. Africanized bees typically immediately charge at a source of disturbance or threat. European honey bees, in contrast, will tend to cluster together and remain in the nest rather than actively retaliate. This makes them easy targets for hungry predators. If disturbed Africanized bees immediately take flight and fly at the threat. Even queens involved in egg-laying are able to take flight. Workers gather around queens in swarms, and either attempt to repel the intruder or opt to leave the hive and abscond to a new nest site.
During foraging Africanized workers move in quick jerky patterns, rather than the steadier, systematic movements of European bees. This pattern of movements makes their courses much less predictable and the chance of their being intercepted in flight is reduced. Killer bees are far more nervous than domesticated bees. They move from flower to flower much more rapidly, almost as though agitated. They are much more industrious than domesticated bees. They begin to forage for nectar and pollen much earlier in the morning, and continue to do so until much later into the evening. When beekeepers open up a hive of killer bees, almost all the bees in the hive take flight. The flight from one hive frequently will trigger flights from adjacent ones. These bees are not necessarily in an aggressive state, but merely nervous.
Finally there are a number of other differences between the two types of bees. Keep in mind that the European bee is a domesticated animal and human have breed for a number of characteristic that are beneficial to modern beekeeping. For example the use of excessive amounts of propolis has been bred out of some strains of European bees while Africanized bees use copious amounts of this material.
Africanized Bee Replacement of European Bees
Very importantly, killer bees tend to out-compete and genetically replace domesticated bees when both are present in a geographical area. There are a number of reasons for this. In areas where both types are present, wild killer bee hives are much more common than are those of domesticated bees. Studies in Brazil indicate that in the bush there are over 200 wild hives per square mile, while there are only 3 to 4 domesticated hives. This abundance of wild hives is due to the fact that killer bees tend to swarm much more often than domesticated bees and swarms will occupy nearly any type or size of cavity to establish a permanent home. With such an advantage in numbers, killer bees, as a race out-compete domestic bees for available nectar and pollen.
A second reason why Africanized bees replace genetically domesticated bees occurs during swarming. A swarm of killer bees occasionally will enter a beehive and kill the domesticated queen and take over the hive. This behavior is never seen in European bees.
A third possible reason is associated with the mating of the queen. Africanized drones are wild animals while European drones are domesticated. When a virgin queen reaches a drone congregation area that contains both types of drones, there is a high probability that a wild drone will catch her rather than will a domesticated drone. Domestication of animals typically reduces vigor and it makes sense that the wild drone would be a faster flier. Africanized drones also take full advantage of these meetings by arriving earlier and remaining later in the drone congregation areas than European drones.
Africanized drones are also produced in greater numbers than are European drones. In European colonies, drones are produced only until their numbers have reached a certain level (usually in the spring of the year). Production then ceases and drones remain in the hive until the season is over. At the end of the season they are typically driven form the hive or starved to death by worker bees inside the hive. In contrast, Africanized drones are produced continuously. At a certain age, they are forced out of the colony and replaced by younger drones. The older Africanized drones, present in ever increasing numbers, frequently drift into European colonies where they outnumber local drones and inhibit their production. Soon they are mating with European queens and the result is proliferation of Africanized drones by European queens and Africanization of the colony. Africanized males have an advantage over European males in part due to sheer numbers.
Finally, Africanized bees have a slightly shorter life cycle (including queens) than the European stock. In areas where both types of bees occur it is not uncommon to have a mixed gene pool from each within different individuals in a colony. As a result if several queens are being raised within a colony some may carry Africanized bee characteristics and others European bee characteristics. It would follow the first to emerge from the pupae would be an Africanized queen (shorter life cycle). And we know, she would immediately go to those cells containing the remaining queens and kill them--thus selecting for Africanization of the hive.
Aggressive Behavior and Stings
Most importantly, killer bees are much more aggressive than domesticated bees. There have been a few human deaths (in the US) due to these bees in all areas where they occur. The first human death in the United States was recently recorded on July 8, 1993 in Texas. These deaths are associated with mass stinging.
The reason why Africanized bees are more aggressive (Figure 9) than European bees is simply that they have not been domesticated while the aggressiveness of European bees has bee greatly reduced (Figure 10) through selective breeding. It is well-documented that aggressiveness in bees is genetically linked. Of course European bees have been kept in hives for hundreds of years and scientists and bee keepers have selective bred them for non-aggressiveness as well as many other characteristics. On the other hand, the Africanized bee is basically a wild bee with the inborn instinct to protect its hive. It has been suggested that in Africa there have been a number of factors that actually increased and selected for the aggressiveness of these bee over the years. Due to a high level of predation on the hives it would follow that aggressive hives would more likely survive than less aggressive hives thus increasing the aggressive gene in the overall gene pool of the species. Even humans may have been involved in this selective process. In Africa wild hives are frequently raided by humans not only for their honey but also their wax. Again this activity would more likely occur on non-aggressive hives.
Figure 9. Bee keepers covered by Africanized in a very aggressive-stinging state. Image courtesy of USDA Archives.
Figure 10. Some non-aggressive (I hope) European bees. Image courtesy of Robert Matthews, University of Georgia.
Not all the recorded deaths have been due solely to the aggressive behavior of these bees. The press has reported much about the detrimental effects these bees have had on the South American agricultural community. In response to these reports, there have been cases where citizens in South America have decided to take matters into their own hands and have attempted to destroy killer bees hives with axes, guns and cars.
In addition, it is not known why, but killer bee swarms occasionally land on people. This behavior is never seen in domestic bees. These swarming bees are not necessarily aggressive. However, the average person would not remain calm if 40,000 bees in the form of a ball landed on some part of his or her body. A violent reaction could trigger alarm pheromone to be released by the bees, resulting in massive stings. An important factor to remember is that this aggressiveness is a defensive reaction of the bees in order to protect their hive from intruders. Killer bees will not hunt down and attack people as is frequently believed.
This aggressive behavior has been studied extensively. One simple measure that has been used to compare aggressiveness of different bees is to jiggle a 2-inch square section of black velvet cloth on a string in front of a hive for up to 30 seconds. The number of stings in that interval is recorded and the cloth is then dropped on the ground and slowly dragged away measuring how far the bees will follow in order to attack it and the researcher. With the average domestic beehive, no stings would be recorded in the thirty-second interval and, in cases where the bees would begin to attack; they typically would follow for only 100 yards or less. In one extreme case with killer bees, the researcher walked up to a calm hive, dropped the cloth in front of the hive and within five seconds there was a ball of bees the size of a baseball attacking the cloth. Because there was a nearby village, the experiment was discontinued for fear of attacks on villagers, but the bees followed the cloth, attempting to sting it and the researcher for 1/2 mile.
With Hymenoptera, which includes wasps, bees, and ants, the stinger is a modified egg-laying apparatus (ovipositor) and since male don’t lay eggs only the females can sting. Most types of Hymenoptera are solitary insects and typically do not sting unless provoked (e.g. touching or stepping on them). Yellow jackets, bumble bees, honey bees, and fire ants are social insects and are protective of their colonies. There are specific individuals in their colonies whose function is to defend the nest vigorously. For example, in a honeybee colony a few dozen of the worker bees are designated as guard bees. They typically guard the entrance of the hive against intruders. One of the reason bee keepers smoke hives prior to inspection is to pacify these individuals. When a bee hive is smoked this causes the bees to fill their stomachs with honey. Apparently this bloating with honey reduces the ability of bees to sting. Also smoke tends to reduce the ability of bees to perceive the alarm pheromone. Foraging bees are typically far less aggressive than hive bees as they lack the instinct to protect the colony. These bees will normally only sting if they are disturbed (rarely so) or injured as they go about their activities.
An individual Africanized bee can sting only once and has the same venom as the European honeybee. However, Africanized honey bees are less predictable and more defensive than European honeybees. They are more likely to defend a greater area around their nest, and they respond to a disturbance faster and in greater numbers than the European honey bee.
The major chemical that causes the pain from a honeybee sting is called melittin; it stimulates the nerve endings of pain receptors in the skin resulting in an initial sharp pain that lasts a few minutes and later turns into a dull ache. The affected area may remain sensitive to the touch for a few days.
The victim’s body responds to stings by releasing fluids from the blood which function to attempt to flush venom from the affected area. This typically causes redness and swelling at the sting site. If the victim has been previously stung by a bee (or other insect), the immune system may recognize the venom and increase the disposal procedure. This can lead to very large swelling around the sting site or the whole body. The area is quite likely to itch. Oral and topical antihistamines should help prevent or reduce the itching and swelling. It is advisable not to scratch the areas as surface bacteria may be introduced into the wound resulting in a secondary infection.
The stinger of a honeybee and Africanized bee is barbed and is pulled from the bee’s body and imbedded into the victim. A bulbous poison sac, sting musculature and part of the digestive system are included with this gift from the bee. Of course it is well known that once a bee stings, its fate is sealed as it will soon die. The stinger is a double bladed structure and, once injected, will continue to work its way deeper into the skin for a minute or more. During the same time interval the poison from the poison sac is pumped into the body. As a consequence, it is important to remove the stinger as quickly as possible in order to reduce the amount of venom injected into the wound. There are several theories as to how to properly remove a bee sting, but recent studies indicate that it doesn’t matter how you get it out as long as it is removed as soon as possible. If removed within 15 seconds of the sting, the severity is reduced.
A small percentage of the population is allergic to wasp or bee stings. In many cases these are inherited or genetically linked. Such reactions can take many forms including less serious maladies such as hives, swelling, nausea, vomiting, abdominal cramps, and headaches. Life-threatening reactions such as shock, dizziness, unconsciousness, difficulty in breathing, and laryngeal blockage resulting from swelling in the throat require immediate medical care. Symptoms can begin immediately following the sting or up to 30 minutes later and may last for hours.
With allergic situations, the venom circulating in the body combines with antibodies that are associated with mast cells resting on vital organs. As a result the mast cells release histamine and other chemicals resulting in a leakage of fluid out of the blood and into the body tissues. Blood pressure drops dangerously low and fluid builds up in the lungs. If this response is not reversed within a short time, the patient may die of anaphylactic shock.
Anaphylaxis, if treated in time, usually can be reversed by epinephrine (adrenaline) injected into the body. Individuals who are aware that they are allergic to stings should carry epinephrine in either a normal syringe (sting kit) or in an auto-injector (Epi-Pen) whenever they think they may encounter stinging insects. Epinephrine is obtainable only by prescription from a physician. Antihistamines potentially have value in combating non-life-threatening reactions, but should be used according to a physician’s instructions.
Another method of combating allergic reactions is the process of desensitization. In this approach, the patient is subjected to injections of the venom to which he or she is allergic in increasing doses over a period of time. Like hay fever shots, this tactic is to build up a protective concentration of antibodies in the blood that will intercept and tie up the venom components before they can reach the antibodies on the mast cells. Desensitization with pure venom works about 95% of the time.
On rare occasions a victim may receive multiple stings. This can occur from the European or Africanized bee. With European bees there are very few cases where a victim receives over a few dozen stings at any one time and almost all of these are associated with careless bee keepers. Since the Africanized bee tends to protect its hive much more rigorously and over a larger distance from the hive than the European bee, mass stinging is more likely to occur from this insect.
Depending on the number of stings, the results can be quite similar to those describe above in non allergic situations. I have received multiple stings on several occasions (careless stupid professor). On one occasion I attempted to remove a swarm from a new science building that was under construction. I was successful in placing the swarm in a hive but while carrying it to the back of the roof of the building a construction worker jarred the hive and released the hostile bees. Unfortunately I did not have a bee suit on at the time and there was total panic on the roof as the bees were beginning to attack the construction workers. I had a choice of bailing or carrying the hive to the other (vacated) end of the building. Since I didn’t want anyone diving off the 4 story building I chose the latter. On the journey I receive approximately 30 stings to the head. Ensuing symptom included a severe headache and a dizzy feeling or rather nice buzz!
Multiple stings have the potential of killing. In the case of humans, the toxic dose (LD50) of the honeybee venom is estimated to be 8.6 stings per pound of body weight. Obviously, children are at a greater risk than adults. In fact, an otherwise healthy adult would have to be stung on an average of over 1,000 times to be in risk of death. Most deaths caused by multiple stings have occurred in men in their 70s or 80s who were known to have poor cardiopulmonary functioning and less capability of escaping an attack.
A second, potentially life-threatening result of multiple stings occurs days after the incident. Proteins in the venom act as enzymes: one of which dissolves the cement that holds body cells together, while another perforates the walls of cells. This damage liberates tiny tissue debris that would normally be eliminated through the kidneys. If too much debris accumulates too quickly, the kidneys become clogged and the patient is in danger of dying from kidney failure. It is important for persons who have received many stings at one time to discuss this secondary effect with their doctors. Wasp stings are as potent in this respect as bee stings. Patients should be monitored for a week or 2 following an incident involving multiple stings to be certain that no secondary health problems arise.
As seen by Figure 11 the number of deaths due Africanized bee stings in the US is quite small. Actually the chances of someone being killed by these insects is less than the chance of being killed by lightning. A record that is not readily available is the number of pets (especially dogs) that have been killed by these bees. This number would be significantly higher although still not alarmingly large. The difference is that dogs that are enclosed in a backyard can not escape from attacking bees.
Again note the age of the individuals killed. A major factor here is that old people cannot run as fast in attempting to escape. The first US death attributable to AHB was in Texas on 15 Aug. 1993 when an 82 year old man attempted to burn a colony out of a house and was stung 40 times. The second fatality occurred on 11 June 1994. An AHB colony was disturbed by a lawn mower, and as the operator ran to escape, he passed by a 98 year old man who was stung about 50 times and died 2 days later. These two deaths are unusual because death due to the venom itself (rather than allergic response or heart attack precipitated by the attack) for adults in good health would usually require more than 300 stings (some people have survived more than 1000 stings). They highlight the fact that elderly people and children are most at risk from bee attacks.
Figure 11. Deaths due to stings of Africanized bees in the United States.
The chance of encountering a colony of Africanized bees is extremely small. In most cases this would only occur with a wild or feral colony as most bee keepers are well aware of the existence of these bees and take precautions to prevent their establishment in their hives. The homeowner can also take certain precautions to prevent possible problems from these bees.
1. One way to prevent bees from establishing a colony on a property is to not provide them with an ideal environment for survival. The availability of shelter is especially important. As discussed the Africanized bee is far less selective about what it calls home than its European counterpart. Common nesting locations include water meter boxes, metal utility poles, cement blocks, junk piles, overturned flower pots, old tires, mobile home skirts, and abandoned structures. Holes in the ground and tree limbs, mail boxes, even an empty soda pop cans are possible locations. Remember, Africanized honey bees also nest in a wide variety of locations and may enter openings as small as 3/16-inch in diameter (about the size of a pencil eraser) as long as there is a suitable-sized cavity behind the opening for a nest.
2. Because honeybees nest in such a wide variety of locations, be alert for groups of flying bees entering or leaving an entrance or opening. Listen for buzzing sounds. Be especially alert when climbing, because honey bees often nest under rocks or within crevices within rocks. Don’t put your hands where you can’t see them.
3. If you find a colony of bees, leave them alone and keep others away. Do not shoot, throw rocks at, try to burn or otherwise disturb the bees. If the colony is near a trail or near areas frequently used by humans, notify your local office of the Parks Department, Forest Service, Game and Fish Department, even if the bees appear to be docile. Honeybee colonies vary in behavior over time, especially with changes in age and season. Small colonies are less likely to be defensive than large colonies, so you may pass the same colony for weeks, and then one day provoke them unexpectedly.
4. Wear appropriate clothing. When hiking in the wilderness, wear light-colored clothing, including socks. Avoid wearing leather clothing. When they defend their nests, honeybees target objects that resemble their natural predators (such as bears and skunks), so they tend to go after dark, leathery or furry objects. Keep in mind that bees see the color red as black, so fluorescent orange is a better clothing choice when hunting.
5. Avoid wearing scents of any sort when hiking or working outside. Africanized honeybees communicate to one another using scents and tend to be quite sensitive to odors. Avoid strongly scented shampoo, soaps, perfumes, heavily scented gum, etc. If riding, avoid using fly control products on your horse with a "lemony" or citrus odor. Such scents are also known to provoke or attract honeybees.â€¢
6. Be particularly careful when using any machinery that produces sound vibrations or loud noises. Bees are alarmed by the vibration and/or loud noises produced by equipment such as chain saws, weed eaters, lawn mowers, tractors or electric generators. Honeybees may also be disturbed by strong smells, such as the odor of freshly cut grass. Again, check your environment before you begin operating noisy equipment.
7. Keep in mind that many more pet are attacked by Africanized bees than are humans. When hiking it is best to keep your dog on a leash or under close control. A large animal bounding through the brush is likely to disturb a colony and be attacked. When the animal returns to its master, it will bring the attacking bees with it. At home, be careful not to tie or pen animals near honeybee hives. The animals receive numerous stings because they can’t escape the bees. If your animals or pets are being stung, try to release them without endangering yourself.
If someone is attacked by Africanized bee the best thing he or she can do is run. Don’t fall to the ground and attempt to cover up but run in a straight line (not zig-zag). Passing through low hanging vegetation will frequently confuse bees and possible break off their attack. Try to get indoors or into a car. In the latter case you may take a few bees with you but once in enclosed situations bees tend to sting less. It is not difficult to out run bees (from experience) but in the case of Africanized bees they may follow you for a considerable distance (several hundred yards). It is not advisable to jump into water in attempting to avoid attack from these critters. There have been cases where the attacking bees waited for a victim to come up for air and followed his or her carbon dioxide trial down into the throat and deeper.
New California Laws Pertaining to Control of Africanized Bees
On January 1, 1995 Senate Bill 250 (Sponsored by San Diego County and the California Cooperative Africanized Honey Bee Task Force) creating a voluntary certification training program in the control of Africanized Honey Bees for licensees of the Department of Pesticide Regulation and the Structural Pest Control Board became effective.
The new laws created by Senate Bill 250 recognizes licensees as experts in the control of Africanized Honey Bees, if they complete the "Africanized Honey Bee Certification Training for Structural and Agricultural Pest Control Operators" developed by the Governor’s Africanized Honey Bee Task Force in cooperation with Pest Control Operators of California.
The "Africanized Honey Bee Certification Training for Structural and Agricultural Pest Control Operators" is completely voluntary in nature. The AHB Certification Training establishes a standard for evaluation of licensees and the public). Once trained these individuals are "officially" experts in the field of Africanized Honey Bee Control.
The New Africanized Honey Bee Statutes
Section 8565.6 of the Business and Professions Code:
"An applicant for a Branch 2 license may elect to be certified in the handling, control and techniques of removal of Africanized honey bees. The board shall develop a program to certify applicants in this specialty, or may approve a program for certification developed by the Pest Control Operators of California."
- In November of 1994 the Department of Consumer Affairs, Structural Pest Control Board officially adopted Africanized Honey Bee Certification Training for Structural and Agricultural Pest Control Operators offered by Pest Control Operators of California as the only authorized certification program.
Section 12203 (c) of the Food and Agriculture Code:
The director may develop a training program that covers the handling, control , and techniques of removal of Africanized honey bees or may approve a training program developed by the Pest Control Operators of California or any other equivalent training program subject to the following requirements:
(1) A certificate of training shall be presented by the training provider to the applicant upon completion of the approved training program.
(2) Providers of approved Africanized honey bee training shall submit to the director a list of those persons who have completed the training, including, but not limited to, the following information:
(A) The full name of each person who has completed the training.
(B) The license or certificate number of each person who has completed the training, if the person trained is licensed by the Department of Pesticide Regulation.
(3) The providers of approved Africanized honey be training shall maintain a record for three years of the individuals who have completed the training.
Section 14153 (c) contains the exact same language as in Section 12203 (c). The difference is that Section 12203 deals with the issuance and licensing categories of Qualified Applicator Licenses, and Section 14153 deals with the issuance and licensing categories of Qualified Applicator Certificates.
Africanized Honey Bee Certification for Structural and Agricultural Pest Control Operators offered by Pest Control Operators of California is currently the only program authorized by 12203(c) and 14153(c).
More than 1600 licensees and government officials have completed Africanized Honey Bee Certification Training for Structural and Agricultural Pest Control Operators which was first offered in January 1994. Lists of the licensees who have completed the program are being made available to county agricultural commissioners and other interested government bodies. (Soon this information will be available on this website) Each licensee is classified by the type of bee control that they offer, and the licensees that they have. The following outlines the different bee control classifications:
Classification of Bee Control Licenses
Non Structural Only:
a) Controlling swarms, and hives in non structural areas only requires the appropriate DPR license
Partial Structural Only:
a) Controlling swarms and hives in structural areas only, but not removing hives from wall voids requires Structural Branch 2 license
Complete Structural Only:
a) Both controlling swarms and bee hives in structural areas
b) Removal of hives from wall voids. requires Structural Branch 2 license
Partial Structural and Non Structural:
a) Controlling swarms and hives in structural and non structural areas
b) No removal of bee hives in wall voids requires Structural Branch 2 license and appropriate DPR license
Full Service AHB Experts:
a) Controlling swarms and hives in non structural areas
b) Controlling swarms and hives in structural areas
c) Removal of hives from wall voids requires both a Structural Branch 2 license and appropriate DPR license.
The Red Imported Fire Ant
There are many species of fire ants in the United States, but the most serious pests are 4 in the genus Solenopsis: the red imported fire ant, the black imported fire ant, the southern fire ant, and the fire ant. Distinguishing between imported and native species of fire ants is difficult, even for experts. Identification usually requires 40 or more randomly collected worker ants for study.
Black Imported Fire Ant
The black imported fire ant, Solenopsis richteri, is very similar to the red imported fire ant. Its current distribution is limited to a small area of northern Mississippi and Alabama. It may be displaced from established habitats by the red fire ant. Scientists have long thought that the black and red fire ants were 2 distinct species. Recently it has been discovered that hybrids of these ants produce viable offspring, and some scientists now wonder whether they are simply 2 races of the same species, varying in color and perhaps behavior.
Southern Fire Ant
The southern fire ant, Solenopsis xyloni, is a native species that occurs from North Carolina south to northern Florida, along the Gulf Coast and west to California. In California it occurs in the lower altitudes from Southern California up through Sacramento but is seldom found along the coast in central to northern California. This is probably our most common native species of ant but its distribution is greatly retarded when the Argentine ant is present. However in areas where the Argentine ant is controlled, populations of this species rapidly return.
Colonies may be observed as mounds or more commonly may be constructed under the cover of stones, boards, and other objects or at the base of plants. These ants also nest in wood or the masonry of houses, especially around heat sources such as fireplaces. Nests often consist of loose soil with many craters scattered over 2 to 4 square feet. In dry areas nests may be along streams, arroyos, and other shaded locations where soil moisture is high. Southern fire ants usually swarm in late spring or summer.
The workers are very sensitive to vibrations or jarring. If their nest is stepped on they will rush out and sting the feet and legs of the intruder. Individual reaction to their venom is quite variable depending on allergic reaction. There is a least one case of a human infant death due to mass stinging of this species.
This species is practically omnivorous feeding on a variety of materials including honeydew, meat, seeds, fruit, nuts, cereal and cereal products, grease and butter and dead and living insects. It can be quite detrimental to agriculture foraging for seeds from seed beds, girdling nursery stock, and consuming fruits and vegetables. In addition these ants will remove insulation from wiring and occasionally gnaws on a variety of fabrics.
The fire ant, Solenopsis geminata, is a native species sometimes called the tropical fire ant. It ranges from South Carolina to Florida and west to Texas. It is very similar to the southern fire ant except its head is much larger and the petiole node is higher and narrower. This species usually nests in mounds constructed around clumps of vegetation, but may also nest under objects or in rotting wood.
Red Imported Fire Ant
The red and black imported fire ants were first reported in the United States in 1929. It is thought that they came to the port in some soil used as ballast in the bottom of a cargo ship. Since this introduction the black fire ant has not spread as rapidly as the red imported species. By 1953 (first official USDA survey) the red imported fire ant had spread to over 100 counties in 10 states. Today it is prevalent throughout the southeastern US and has moved into Texas, New Mexico. Arizona and California.
Natural movement of fire ants is limited to mating flight or by rafting during period of flooding. However, the rapid movement of these species across the South and westward is mainly associated with human activity. In this case the initial spread of these ants in the southeastern US was thought to be due to movement of sod and potted ornamental plants. This inadvertent movement of S. invicta and S. richteri was noted by the U.S. Department of Agriculture in 1953 when a direct link was established between commercial plant nurseries and the spread of imported fire ants. In response to mounting public pressure, the U.S. Congress appropriated $2.4 million in 1957 for control and eradication efforts. As part of an overall plan quarantine was imposed to retard or prevent the artificial dissemination of these now notorious pests. On May 6th 1958, regulations governing the movement of nursery stock, grass sod and some other items were instituted through the Federal Quarantine 301.81. By that time, however, imported fire ants had moved into 8 southern states. This spread, although slowed considerably by federal regulations and climatic conditions, continues even today. In recent years, isolated infestations of imported fire ants have been found as far west as New Mexico, Arizona California and as far north as Kansas and Maryland. In the case of California it is thought that the spread of these ants into this state was due to movement of bee hives as most initial infestations were found in around orchards and other situations where bees were moved into these areas for crop pollination. Based on USDA prediction these ants have a potential of even expanding the spread throughout much of the United States (Figure 1).
Figure 1. Current and potential distribution of imported red fire ant. Image courtesy of USDA.
Adult fire ants (Genus Solenopisis) are characterized by the presence of a ten-segmented antennae, two-segmented antennal club and two-segmented waste that joins the thorax to the abdomen which is typically darker than the rest of the body (Figure 2). Species identification is somewhat more difficult due to hybridization between the 2 "native" species as well as between the 2 imported species.
Figure 2. Diagram of diagnostic characteristics of red imported fire ant.
A mature colony of fire ants typically consists of 4 main stages: egg, larva, pupa, and adults. Since these are true social insect there is a caste system with different shaped and sized adults that carry out different function within the colony. These adult forms include the polymorphic workers, winged males, winged females and one or more reproductive queens. The egg, larval, and pupal stages (Figure 3) occur within the underground nest and are only seen when nests are disturbed or when they are being carried to a different location by workers (Figure 4). The eggs are small but can be seen with the unaided eye. They hatch into the grub-like legless larvae that are fed by the workers. Ant larvae in general are legless, carrot shaped with a well-developed unpigmented head capsule and are typically hooked at the head end. The larvae will grow and molt (shed their exoskeleton) 3 times prior to molting into the pupae, which are similar in appearance to the adults except that their legs and antennae are held tightly against the body. As with the larvae the pupae lack pigmentation, especially in the early instars. As they mature they begin to turn darker. As discussed in honeybees, the function of the polymorphic workers is determined primarily by age (and to a much lesser degree by size). Younger workers typically care for and feed the brood while middle-aged workers maintain and protect the colony. The oldest workers forage for food.
Figure 3. Egg, larval and pupal stage of fire ants. Image courtesy of USDA Archives.
Figure 4. Worker fire ants carrying larva for relocation. Image courtesy of USDA, Calif. Dept Agriculture.
The alates, or winged reproductives (Figure 5), are most abundant in the late spring and early summer, but can be found at any time of the year. The males are decidedly smaller than the females, glossy black and have a smaller head. Although both winged males and females can be found in the same colony, as a general rule one form will be dominant. It is possible that this functions to increase the chances of one sex mating with another from a different colony. Most colonies in a given area typically swarm on nuptial flights at the same time. This benefits the species and insures mixing of the gene pool. It is well-documented that inbreeding is generally detrimental to a given species.
Figure 5. A winged reproductive of the red imported fire ant. Image courtesy of USDA Archives.
Mating flights most often occur at mid-morning 1 or 2 days following a rainfall if the temperature is above 22°C and the wind is light. At this time a virgin female flies into a cloud of congregating males and mates in the air. The male subsequently dies while the female seeks a location to start a new colony. Once located, she breaks off her wings and excavates a brood chamber approximately 1 to 2 inches below ground. The new queen subsequently deposits a few dozen eggs which hatch in a little over a week. The queen does not forage but feeds the first generation of larvae from nutrients obtained from her fat reserves and by dissolving her no longer needed wing muscles. The larvae obtain the nutrients by trophollaxisis (exchange of alimentary fluids) or from sterile eggs she has produced for that purpose. The entire life cycle is completed in 3 to 4 weeks.
The initial generation of adult worker (minims) are relatively small due to a limited amount of nutrients available from the queen. Once developed these worker open up the brood chamber and begin to forage for available food. Soon another generation of larger adult workers (Figure 6) has developed and the colony begins to grow. Workers start to emerge daily and within 6 months the colony population approaches several thousand and an above ground mound is visible. The polymorphic (poly in Latin means many and morph means form) nature of the worker becomes more apparent. The largest workers in the colony (majors) can be as much as 10 times the size of the smallest workers (media). The queen lives up to 7 years and produces an average of 1600 eggs per day. At maturity, a monogynous (one queen) fire ant colony can consist of over 250,000 ants. As discussed above some fire ant colonies have only one queen per nest while others can have many queens and are called polygynous colonies. The polygynous colony may be more difficult to control because all the queens must be killed to prevent the colony from surviving. Polygynous colonies frequently expand by "budding"; i.e., some of the queens and workers break off from the parent colony and start a new mound nearby. This process in polygynous colonies can accounts for much higher mound density which sometimes approaching 1,000 mounds per acre.
Figure 6. Different sized worker adults. Image courtesy of USDA Archives.
One of the identifying characteristics of an imported red fire ant colony is the earthen nest or mound (Figure 7). This mound is a cone-shaped dome with a hard crust. They averages 1 1/2 feet in diameter and 8-inches in height. In heavy clay soils they can exceed 3-feet in height and 4 1/2 feet diameter. There are usually no external openings in the mound; but tunnels a few inches below the surface tunnels radiate several feet from the mound allowing foraging workers access to the colony. These mounds serves several functions: They act as a flight platform for nuptial flights and to raise the colony above ground in excessively wet soil while protecting it above ground from intruders and rain. They also serve as a passive solar collector to supply warmth to the colony during the cold winter months.
Figure 7. Mound of red imported fire ant. Image courtesy of USDA Archives.
In areas with hot, dry summers these mounds may not be maintained or may not be formed at all. In a dark, protected site with sufficient moisture and an adequate supply of food, fire ants will nest in a wide variety of locations (e.g. rotten logs, walls of buildings, under sidewalks and roads, in automobiles, in dried cow manure).
Fire ants are omnivorous, feeding on almost any plant or animal material; although dead and living insects seem to be their preferred food. In rural habitats, they have a major impact on ground nesting animals (birds, reptiles, mammals). Studies have shown that once established in a new area there is typically a minimum of a two-fold reduction in the populations of field mice, snakes, turtles and other vertebrates and a maximum of a total elimination of some species. Fire ants also feed on plants attacking young saplings and seedlings, destroying buds and developing fruits and have been shown to feed on the seeds of over a hundred species of native wildflowers and grasses.
Damage to plants is increased during periods of drought as fire ants seek alternate water sources. In fields where drip irrigation is used, these insects build their mounds over the emitters reducing or blocking the flow of water to crops. In some cases, actual physical destruction of microsprinkler assemblies has occurred. Finally, the mere presence of fire ants on plants and within the field will deter hand-harvesting of crops.
As an urban pest, imported fire ants cause many of the same problems experienced in rural areas. In addition they nest within the walls of homes and offices. Colonies are established under sidewalks and roadways frequently resulting in complete collapse of sections of these structures if the nests are eventually abandoned. The presence of fire ants can deter outdoor activities in yards, parks and school grounds. Home invasions can threaten small children and the elderly. House invasions are especially prevalent during periods of heavy precipitation and flooding. Fire ant colonies have been found inside automobiles, trucks and recreation vehicles resulting in traffic accidents caused by fire ants stinging the drivers. Imported fire ants are attracted by electrical currents and have caused considerable damage to heat pumps, air conditioners, telephone junction boxes, transformers, traffic lights, and gasoline pumps.
Because of their reputation people fear fire ants. In some areas playgrounds, parks, and picnic areas are rarely used because of the presence of fire ants. In campsites of state and national parks in fire ant infested areas, it is often difficult to put up or take down a tent without being stung by angry ants.
Fire ants are best know for their behavior of stinging, frequently in mass. If a nest is disturbed hundreds if not thousand of ants will quickly emerge and attack the intruder. This occurs so quickly and in mass that is not uncommon to have hundreds on the victim before the first sting is felt. To make matters even worse a single fire ant can sting repeatedly and will continue to do so even after their venom sac has been depleted. Once reaching the victim the ant will typically attach with its mandibles to the skin and then insert its stinger. Subsequently it will rotate it abdomen and repeatedly sting using the attached head as a pivot. The result is a circle of several stings from the same ant.
Initially, the sting(s) result in a localized intense burning sensation (hence the name "fire" ant). Within a day or two a white pustule forms at the sting site (Figure 8). Pustule formation occurs only with the red and black imported fire ant and not the southern fire ant or fire ant. There is a possibility of secondary infection and scarring if the wounds are not kept clean or if they are continually picked at or scratched (Figure 9). As with any other hymenopterous stings, there are a few individuals who are hypersensitive to the venom and can react quite strongly and be severely affected. Symptoms in these cases can include chest pains, nausea, dizziness, shock or, in rare cases, lapsing into coma. In cases of an allergic reaction, even a single sting can lead to a potentially serious condition called anaphylactic shock. There are recorded cases of human death resulting from fire ant stings but these are rare.
Figure 8. Pustular formation for sting of red imported fire ant. Image courtesy of USDA Archives.
Figure 9. Secondary infection of sting from red imported fire ant. Image courtesy of USDA Archives.
Individuals with disabilities, reduced feeling in their feet and legs or reduced mobility, are at greater risk from serious stinging incidents and the incidence of resulting medical problems may be even greater. Large numbers of ants can sting and even overcome victims before they can safely escape. There was a recent case where fire ants entered a room of an elderly gentleman in a retirement hospital and basically stung him to death. In his case he was unable to escape their attack.
Individuals who are known to be allergic to fire ant stings should seek professional advice from a physician or allergist, especially if they are in situations where they might be exposed to these pests. There are emergency treatment kits that are available (by prescription) for individuals who are sensitive to their sting. Fortunately, relatively few deaths from fire ant stings have been documented, especially when compared to deaths from bee and wasp stings. Victims stung to death by fire ants often were not able to escape, sustained large numbers of stings, and suffered allergic reactions to the venom.
There are basically two methods of fire ant control, namely individual mound treatment and broadcast treatment. Before attempting either, it is advisable to check with regulatory agencies as the availability and use of different chemicals for either method may vary from state to state. In addition, in many cases free control by state governmental agencies of these pests is available.
Individual Mound Treatments
Treating individual fire ant mounds can be time consuming, but it is generally the most effective method of control. Once treated it will take anywhere from a few hours to a few weeks before total elimination of a colony depending on the product used, time of the year and size of the mound. Treatment is usually most effective in the spring with the key being to treat all the mounds in the area. If control is not complete, reinfestation of an area can take place in less than a year. There are several different methods that can be used to treat individual mounds.
One of the more commonly used methods is drenching mounds with a high volume of diluted contact pesticide. As with any treatment, it is extremely important to follow label directions not only to attain maximum effect, but to maximize safety of the application and avoid potential illegal consequences. In most cases the mounds and surrounding areas are wetted thoroughly but gently with the drench. Subsequently the mound is broken open and the insecticide is poured directly into the tunnels. Mound drenches are most effective after rains when the ground is wet and the ants have moved up into the drier soil in the mound. During excessively dry weather, effectiveness of the treatment may be enhanced by soaking the soil around the mound with water before treatment. One problem with this technique is that the queen may be too deep to be reached with the drench. This may be especially true if the colony is disturbed prior to an application. In this case the workers may move the queen deeper into the colony in order to avoid a potential threat.
Granular formulations are also available for individual mound treatment. In this case once the recommend dose is applied to the mound it should be watered thoroughly in order to reach the worker ants and queen that occur deeper in the colony. The dissolved granules must come into direct contact with the ants to have any effect. As in mound drenches, care must be taken not to disturb the colony prior to application.
A few insecticides are marketed as injectants. In this case they may be injected using a "termite rig" with a soil injector tip, a standard 1-3 gallon compressed air sprayer with a fire ant injector tip, or a special aerosol soil injector system. The mound is injected in a circular pattern, usually at 3 to 10 points. A new product combines insecticide treatment with high temperature vapors to increase penetration.
Fumigants are readily available in most states for fire ant control. These are usually more effective than surface applications or mound drenches but are also more expensive and can be dangerous if not handled properly.
Depending on the state a number of fire ant baits are available. These can be used for treating individual mounds or for broadcast treatment of larger areas. The bait should be uniformly applied around the mound 0.3 to 1.0 meters away and not on the mound itself. Baits are much slower acting than the control methods listed above but are generally safer, cheaper and more effective in the long run.
The use of boiling water has been examined on several different occasions resulting in varying degrees of success. In one experiment over a 50% of treated mound were eliminated by pouring approximately 3 gallon of hot water directly into the mound. The use of steam produced by a steam generator produced similar results. Regardless both techniques are far less effective the use of drenches, fumigants, granular formulation or baits are cumbersome in the field are not practical when dealing with large populations of these pests. Area wide flooding with water has not proven to be effective, impractical in most situations and can led to spreading of the population due to the rafting ability of these insects.
A number of fire ant baits (Figure 10) are commercially available for broadcast treatments (again depending on the state). Baits are composed of an inert carrier-attractant (corn carrier and soybean oil) and toxicant. The active ingredient (either a slow-acting insecticide or an insect growth regulator) is incorporated into the oil. These baits can be applied either by a hand operated granular fertilizer spreader or larger equipment (Figure 11). Once foragers find bait they carry it back to the nest, ingest it and begin feeding other ants in the nest. Because the active ingredients are slow acting, they are spread around the nest before the desired effect. This formulation and means of application has a number of advantages. Unlike individual mound treatments, colonies need not be "located" in order for them to be treated and as a result this method is less time intensive and consequently less expensive than individual mound treatments. On the other hand broad cast treatment has the potential of affecting non-target organisms. It is also slow acting and the effectiveness of the bait is greatly reduced when they come in contact with water from rain, irrigation or other sources. Finally baits are only effective during those times of the year or temperatures when the ants are readily foraging. Generally speaking it is advisable to only use this type of treatment in areas where there is little or no human traffic. If broadcast treatment is used in such an area, a good choice is growth regulator bait, which poses much less risks to non-target species. For example, fenoxycarb bait has been shown to be very effective for suppression of fire ant populations when applied in one application over a wide area.
Figure 10. A corn-based bait used for control of the red imported fire ant. Image courtesy of USDA Archives.
A tractor driven granular applicator. Image courtesy of USDA Archives.