10 Most Wanted

Ants, bees and wasps fall into the order Hymenoptera. With more than 130,000 named species, they are a contender for the second largest order of insects in the world. Only the beetles (Coleoptera) boast a greater number of species. Most would not dispute, however, that the order Hymenoptera is the most beneficial of all insect orders. The bees, for example, produce honey and wax and are the most important of our pollinators. Many wasps and hornets are magnificent parasites and predators on a myriad of pests. Finally, ants provide a beneficial role in everything from soil aeration to pest predation and even serve as a food source in some cultures.

Unfortunately, one thing that is common to all of the hymenoptera is the presence of a stinger in the females. They normally use this device for laying eggs but it is also used for protection. Venom is injected into their prey through the stinger. Humans and pets often can be stung when they come into close contact with bees, wasps and ants. In fact, more than 500,000 people enter hospital emergency rooms every year suffering from insect stings and 40 to 150 people die as a result of an allergic reaction to these stings.

There are various stinging pests that you may be called upon to manage. Each may require a different approach and different control techniques. Here’s a list of the “10 most wanted” stinging insects with information on their biology and habits and recommendations for control.

FIRE ANTS. These ants belong to the genus Solenopsis and can readily be distinguished from all other ant species in North America by their 10-segmented antennae with a two-segmented club. These characteristics, combined with the presence of a sting, a two-segmented pedicel and a thorax that lacks spines, make identification of the genus relatively easy. The two main species in the U.S. are the red imported and the Southern fire ant. In recent years, isolated infestations of imported fire ants have been found as far west as California and as far north as Kansas and Maryland. These ants commonly nest next to and inside electric appliances, such as air conditioners, heat pumps and even traffic control boxes. Fire ants are omnivorous and will feed on almost any plant or animal material. Insects, however, seem to be their preferred food. In rural habitats, fire ants have a major impact on ground-nesting animals of all types.

While any attempts to control imported fire ants over large areas are currently impractical, there are two basic methods that can successfully control them within a limited area: treatment of individual mounds and broadcast treatments.

Individual mound treatments may consist of liquid, aerosol, granular or bait formulations. Broadcast treatment is the distribution of insecticidal bait over a large infested area containing many fire ant colonies. One disadvantage is that broadcast treatments can disrupt native ant communities as well as fire ant infestations. Broadcast treatments can result in an ant community changing from one that is dominated by native ants to one dominated by fire ants. On the other hand, in areas with high mound densities, broadcast applications allow large areas to be treated quickly.

The key to reducing the threat of fire ant infestations indoors is prevention, which means removing exposed food sources that may attract these insects.

Insecticides labeled for indoor use, particularly pyrethroids, can be used in homes and public buildings to drive foraging ants outside or away from high-use or critical areas, such as kitchens, recreation rooms, patient rooms, operating rooms or intensive care units. Although baits work well for many ants that invade buildings, they should not be used to control fire ants indoors because they are more likely to attract additional fire ants, increasing the chance that an occupant will be stung.

HARVESTER ANTS. Harvester ants, as the name implies, collect and harvest seeds as their primary food source. While harvester ants do not normally enter buildings, their habit of removing all vegetation around their nests can result in large bare areas in lawns. But it’s their sting that gets them included in the “Top 10” of most wanted stinging insects. There have been reported cases of death as a result of numerous stings from harvester ants.

Control can be achieved by treating mounds during the hot part of the day when the ants are in the nest. Baits containing an insect growth regulator can be effective within a few days. High-pressure injection of a suitable insecticide provides faster control. Injection of an appropriate pesticide dust into mound entrances is another possibility. Drenching or liquid injection is not effective because the nests are so deep.

HONEYBEES. Probably the most beneficial insect on earth, honeybees are not generally aggressive and do not search for something to attack. Instead, they are defensive and will attack only whatever seems to threaten the colony. A honeybee colony may number 80,000 individuals and are the only truly perennial wasp or bee colony. It’s been estimated that honeybees pollinate more than 100 agricultural crops and are involved in about 80 percent of the foods consumed by Americans.

Control of honeybees is discouraged and whenever possible you should contact either your local cooperative extension service or a local beekeeper to have them removed. This is especially true of swarmers in the yard. It might also be possible to have them remove hives from walls and attics. Although control of honeybees is discouraged, there are certainly times when it is necessary. Such occasions occur, for example, when they are nesting deep within the walls of structures. If this happens, make every attempt to first locate the nest itself and be certain to locate entryways. Nest location can often be accomplished by knocking on walls and listening for loud buzzing. Pesticide applications should be made at night. Seal any possible entrances prior to application unless the main entryway will be used. If the nest is located some distance from the entrance, a small hole may be drilled through the wall. Note that the next day the dead bees, honey and comb must be removed to prevent problems later with honey seeping through walls or ceilings, or to prevent secondary pest problems such as mice or other insects.

CARPENTER BEES. Carpenter bees are not social bees and do not live in colonies like honeybees. They get their name from their habit of boring into wood to make galleries or tunnels for rearing their young. The adults overwinter, usually in abandoned nest tunnels. Galleries are made by mated females who reuse an old gallery, construct a new one, extend an existing gallery or branch a tunnel off of an old entrance. Weathered, unpainted wood is preferred. Male carpenter bees tend to be territorial and often act aggressively when humans approach; however, they do not have stingers and thus are harmless. Females do have stingers although they rarely sting.

Control of carpenter bees can only be accomplished by treating each individual gallery. Wettable powder, dust, microencapsulated and aerosol formulations work best. Aerosols may well be the most efficient and safest method to treat especially when on a ladder. Galleries need to be left unsealed for at least 24 to 48 hours so the female has sufficient time to be exposed.

Since carpenter bees rarely attack painted wood, a final way to discourage infestation is to have wood painted or sealed.

BALD-FACED HORNETS. Unlike ants or bees, social wasps and hornets build their nests of paper. The bald-faced hornet is about ¾-inch in size and are primarily black with white faces and markings on the tip of their abdomens.

They are distributed throughout the U.S. and build gray, paper carton nests with many compartments and a papery outer covering, which may hang near ground level or high in trees, shrubs, vines, overhangs, sheds, utility poles. They may be out in the open or other times well hidden and are not used the following year. Bald-faced hornets are beneficial and eat many pest insect species. However, a nest near a structure or close to the ground may be a nuisance and may need to be removed.

Control can be accomplished in the following manner: Locate the nest during the day. Apply appropriate registered aerosol through an entrance hole at the bottom of the nest, at night, with only background lighting and using a bee veil.

A suggestion is to position a flashlight on a ladder or some other object opposite from the direction you will approach and treat the nest. This way, if individuals escape when treatment occurs they will head toward the flashlight and away from you. For high nests a bee pole may be used for added safety. The nest should be removed, placed into a plastic bag and discarded to prevent emerging pupae from causing problems.

PAPER WASPS. Often called umbrella wasps, paper wasps construct their nests of paper but do not cover it as do the hornets. The wasps are slender and about ¾-inch long. Coloring combinations include black or brown with yellow or red markings. Paper wasps are semi-social and live in small colonies but without a worker caste. Only inseminated queens overwinter, often hiding beneath siding, soffits, etc., and when one begins to build her nest in the spring, she is often joined by others who assist and become non-reproducing functional workers. The comb-like nest is suspended upside down by a single pedicel.

Like the other wasps, paper wasps are beneficial and control many insect pests. However, control is warranted if the nest is located near human activity. Control is fairly easy and should take place early in the morning or at night when most of the wasps will be on the nest. Treat with a direct spray of aerosol pyrethrins or a pyrethroid and ensure you treat all of the individuals to prevent any from rebuilding nearby. Nests can be scraped off of the surface with a putty knife.

YELLOWJACKETS. An old German proverb says “God made the bee but the Devil made the wasp.” No doubt it refers to the yellowjacket. As their common name implies, they are primarily black with yellow markings. Two types of yellowjackets occur in the United States; aerial yellowjackets, (Dolichovespula arenaria) and several species of ground-nesting or concealed-nesting yellowjackets (Vespula spp.).

Ground-nesting yellowjackets commonly build in rodent burrows, but other protected cavities like voids in walls and ceilings of houses sometimes are selected. Aerial yellowjackets build nests that are attached to the eaves of buildings or hang from the limb of a tree. The entrance is normally at the bottom of the nest. As with the other social wasps, colonies are started by a single reproductive female and can reach populations of between 1,500 to 15,000 individuals. Like the bald-faced hornet, the nest is enclosed in a paper covering and has a single entryway.

Control of yellowjackets is similar to that of bald-faced hornets. Care should be taken to treat at night if possible. Ground nests may be treated with an appropriate insecticide. A 6-inch area around the entry may be dusted prior to treating inside the entry hole. A brick or rock should then be placed over the entry and left in place until the following day. In the case of nests behind walls in trees, aerosols work best. Note that using baited traps can be an effective way of reducing populations and great success has been achieved although this method is somewhat slower than treating the nest directly.

SOLITARY WASPS. Other solitary wasps include mud daubers, digger wasps, mason and potter wasps. Most are of little importance, but a few can be encountered in significant numbers or in locations where the customer wants them removed. Mud daubers and digger wasps are two such species. Mud daubers, it seems, often build their mud tube nests under overhangs near doorways. The female provisions the tubes with paralyzed spiders and lays an egg before sealing up each cell. Digger wasps get their name from the fact that the female digs into the ground to locate scarab beetle larval hosts. They can be nuisance pests in lawns and can be seen flying back and forth 4 to 6 inches above the surface.

Mud dauber adults can be treated with various insecticides as they land on the mud tubes. The mud tubes can then be scraped down and disposed of. Treating digger wasps can be accomplished by applying an insecticide to the lawn to give rapid knockdown. Long-term control involves treating the lawn to control the grubs that the wasps are feeding on. Again, remember that these are beneficial insects and should be controlled only if necessary.

CICADA KILLERS. The largest solitary wasp in North America (often nearly 1¾ inches in length), the cicada killer gets its common name from the fact that it provisions each of its nest cells with a cicada as food for its young. They are solitary wasps and both males and females can be found flying over a lawn.

They do not share the same nests. Females dig burrows about ½ inch in diameter and as much as 10 inches deep. She then places one or two cicadas that she has captured and paralyzed with her sting and lays an egg on one of them. The larva then feeds on the cicadas.

Again, although beneficial, it is sometimes necessary to control cicada killers. This may be accomplished by dusting the bare nesting area with an appropriately labeled insecticide. After the adults are killed, the nests may be treated with a residual insecticide to ensure that the larvae are also killed.

VELVET ANTS. Though actually solitary wasps, velvet ants get their common name from the fact that the female is wingless and resembles a large hairy ant. They are also nicknamed cow-killers or mule-killers because of their potent sting. Color is black with large areas of red, yellow or white. The larvae are external parasites on the larvae of bees, wasps and a few species of beetles and flies. The wingless females can be seen running on the ground, especially on bare, sandy areas in search of ground-nesting bees and wasps. They will occasionally enter structures in search of prey.

Control of velvet ants is rarely warranted and no pesticides are labeled for them. If one is found indoors, trapping and releasing outdoors is probably the best approach. However, applying a microencapsulated or wettable powder formulation to lawns may discourage ground-nesting bees and wasps and thus discourage velvet ants.

CONCLUSION. Stinging insects of the order Hymenoptera are among the most beneficial of all insects. Honey, wax, pollination and predation or parasitism of many pests species are but a few of the many positive benefits provided by this diverse group. However, it becomes necessary at times to manage these insects to prevent serious injury or even death to humans and pets. When this becomes necessary, you are called upon to step between the customer and the stinger. With the information in this article, I hope you are now prepared to defend.

The author is technical director for the National Pest Management Association and can be reached via e-mail at mlacey@pctonline.com.