Other members of the order Hymenoptera, besides the ants, can become serious pest in and around our parks, homes, or other structures. The pest management professional will encounter these pests from time to time, especially during warmer periods of the year. Some are pests primarily because people are disturbed by their presence, while others are important because their presence in or near inhabited structures represents a true health and safety risk t people and pets.
Some wasps species are social and live in colonies, while others are solitary. Social bees and wasps develop colonies similar to those of ants. These colonies have a queen that produces all the eggs, workers, and brood. The social wasps that will be discussed belong to the family Vespidae and include the paper wasps, hornets, and yellowjackets.
Solitary wasps do not have a colony group. The adult female builds a cell for each egg that she lays and provisions each cell with insect or spider prey for the larvae to eat. There are several families of solitary wasps, but the species most commonly encountered by pest managers belong to the family Sphecidae. These include the mud daubers and digger wasps.
As with bees, female wasps have their ovipositor, or egg-laying structure, modified into a stinger. Wasps differ form bees in that most feed their young on animal matte, such as insects, spiders, or meat particles, and not on pollen. Bees also have hairy bodies, while wasps tend to have smooth and apparently hairless bodies. Professionals will occasionally be called on to control colonies of social bees, such as honey bees (family Apidae) or bumble bees (family Bombidae). Carpenter bees (family Xylocopidae) resemble large bumble bees but have solitary nesting behavior.
The most common hymenopterous pest species that may harm people directly include certain bees and wasps. In contrast to most of our North American ants (except fire ants and harvester ants), these bees and wasps are frequently dangerous because of allergic response to their painful stings. Stinging behavior is generally a defensive reaction, which can occur either when the colony is threatened near the nest area o the individual bee or wasp is trapped and threatened. Foraging wasps of some species are more likely to sting people at some times of the year than others. For example, yellowjacket workers are more apt to sting people during the latter part of their annual cycle, in August or September, for much of the northern part of the United States.
The stinging process includes injection of a rather potent venom. For some species, especially from the family Sphecidae, the venom serves the function of paralyzing or subduing prey, but sings of these wasps are not dangerous to people. In addition to causing intense pain, vespid wasp or social bee venoms contain proteinaceous materials that can cause severe allergic reactions in some individuals. Some people may even go into shock and die of suffocation as their lungs fill with fluid after being stung by a social bee or social wasp. Fortunately, the percentage of our population allergic these venoms is quite low, probably less than 1 percent.
Wasps and bees are considered beneficial insects in most circumstances. Control measures are justified only on the basis of problems these insects may be causing in each given instance. Control usually becomes necessary when a nest is located in a poor location relative to the safety, comfort, or other interests of people. When social wasps or social bees are nesting in locations such as under the front steps of a home, in a school playground, or near the pole supporting a clothesline, an imminent hazard is created, and control is warranted.
Wasps, Hornets, and Yellowjackets (Family Vepsidae) – The most dangerous species of stinging Hymenoptera are wasps of the family Vespidae. A useful characteristic that aids in field identification of vespid wasps is that they fold their wings lengthwise when at rest, making the wings seem only half as wide as they actually are. They also hold their wings separately, often parallel to the body, when at rest.
These wasps are social insects that build nests of a paperlike material, call carton, which is a mixture of wood fibers and the salivary secretions of the female wasps. Queens are inactive during the winter, hiding in protected niches under tree bark or in stone walls, attics, and other sheltered places. In early spring, overwintering queens-called foundresses, since they establish, or found, the new nests and colonies each year – visit exposed surfaces, such as raw and weathered wooden fences or siding, or dead tree limbs where the bark has sloughed away. They chew away wood fibers and combine them with salivary secretions to form the paperlike carton for nest construction.
The nest is begun by the foundress as she builds a small number of cells and places an egg in each. After the eggs hatch, larvae develop within the cells and are completely dependent upon the queen for food. The queen forages outside the nest and brings food back to the larvae, caring for them in this way until pupation occurs. Food for the larvae is protein, usually in the form of caterpillars or other insects. Adult wasps feed on liquids such as nectar, honeydew and juices fro the bodies of insects fed to larvae. After the first sterile female workers emerge, these workers take over the nest building and broodrearing, and the queen stays on the nest. Workers are adult females as far as the structural features of their bodies are concerned, but their internal reproductive organs do not develop.
Only one egg-producing queen will be present in the colony. The workers protect and maintain the nest, forage for food and water, and care for the immature stages or brood (i.e., eggs, larvae, and pupae). Typically, adult males and fertile females are produced by the colony during late summer or early fall. After mating, the colonies die off and only the newly mated queens will find a protected location to overwinter.
If the overwintering queen is able to survive the winter (many do not), she will try to start a new nest and found a new colony during the next spring.
Paper Wasps – (Polistes spp) – The wasp build rather simple nestPaper Wasp consisting of only one tier or layer of cells. The cells open downward and are not covered. Collectively, this layer of cells is generally called a comb. Nests are usually suspended beneath horizontal surfaces, and commonly hang from eaves of houses and beneath window ledges or porch roofs. Polistes nest are rather small, rarely over one foot in diameter, so there are seldom more than 100-200 workers on the nest at any one time. Eastern species are typically a dusky brown color, marked with various shades of orange, or blackish with yellow markings. Western species tend to be somewhat more strikingly colored, with the orange or yellow more predominant.
Hornets – (Vespa and Dolichovespula spp.) Some of the most universally recognized and fearfully provoking social wasp nest are the large grayish-brown carton structures often seen hanging from a tree or bush. These nest generally resemble a very large, inverted tear- drop or a “bloated” soccer ball. The wasps which build such nests are commonly referred to as hornets, but are really yellowjackets. The nest consist of several tiers of carton cells, each similar to the single tier of the Polistes nest in appearance. A continuous paper envelope surrounds the whole nest. There is generally a single opening at the lower tip of the nest. As the nest approaches its final size, the new combs are built below the level of the opening, which will then be positioned on the side of the nest.
The bald-faced hornet, Dolichovespula maculate, moderately largeBaldfaced Hornet and has whitish or yellowish markings on the front of the head, between the eyes. The basic color of the body is black. While aerial nesting wasps in the genus Dolichovespula are considered yellowjackets by most U.S. experts, they can be distinguished from the gorund or structure-nesting yellowjackets of the genus Vespula by the noticeable separation between the lower margin of the eye and the base of the mandible.
The European hornet, Vespa crabro germana, is the largest paper wasp and the only true hornet present in the United States. Its body is brownish and marked with orange. This species was introduced along the Atlantic coast and has extended its range slowly into the Midwestern states. It does not build exposed nests, but nest in natural cavities such as hollow logs or stumps, or in cavities within buildings.
Yellowjackets (Vespula spp.) – Yellowjackets are the smallest (about ½-inch long) of the commonVespids. Most species typically buildYellow Jackets their nests underground, so workers will come and go from the nest via an earthen tunnel which ends in a hole at the soil surface. Underground nests are often started in an abandoned mammal burrow or a similar underground cavity. The nest is expanded initially to fill the cavity, and then enlarged as the colony develops. Particles of earth and small stones may be pile up around the opening of a burrow which houses a large colony of an underground nesting species. Yellowjackets will often utilize available openings at or near ground level. Situations are known in which yellowjackets have built extensive nests within voids of concrete block foundations, or below railroad ties used in landscaping around patios.
A species which commonly nest in structures has spread widely across the northeastern and Midwestern regions of the United States. It is the German yellowjacket, Vespula germanica, which apparently was introduced form Europe into the northeastern U.S. in the Northeast, the German yellowjacket is often found nesting in wall voids, attics, or crawl spaces; and it uses some available hole or crack in the exterior facing of the building as an entry point. This creates difficult control problems for the pest management professional. In the Midwest, the German yellowjacket usually nests in the ground.
Yellowjacket nests resemble hornet nests. As many as several thousand workers may be produced in a colony in one season. Colonies in certain areas of California and southern Florida will persist for more than one year, so are called perennial. These colonies will ultimately develop more workers than typical annual colonies.
Some species of Vespula forage nearly exclusively on live prey such as flies, caterpillars, and other insects, while other species will forage strongly for meat form carcasses, garbage, and picnic tables to feed developing larvae. Yellow jackets also forage strongly on sources of sugars or other carbohydrates such as beer, fruit (i.e., sliced watermelon, and sweet beverages at picnic sites). Workers may also obtain sugars from the honeydew of aphis or scale insects. As new queens are produced in the colony in late summer, they demand sugars from the workers, which then forage aggressively for honeydew and other sources of sugar.
Many experts consider yellowjackets to be the most dangerous of the social Hymenoptera in the United States because of their nesting and foraging behavior, and the prevalence of allergic people.
Nonsocial, or Solitary, Wasps (Family Sphecidae) – Sphecid wasps include only solitary nesting species. This means that a single female builds a nest, or several distinct nests, often with several to many cells each. No carton is used in these nests. Each cell is provisioned with live prey before the cell is sealed. When not flying, Sphecid wasps can be distinguished from Vespid wasps at a distance because they do not fold their wings and hold them separately, but lay on top of the other in a flat position on top of their bodies.
Hornets do not excavate burrows in the ground, but a number of Sphecid wasps are known to do so. The species which is most often mistaken for a hornet is the cicada killer, Sphecius speciosus. It is a very large insect, which may be up to 2 inches long. The body is black and strikingly marked with yellow, so that its general appearance bears some resemblance to a large hornet. The female wasp excavates a large burrow about ½ inch in diameter. Soil is known out of the burrow, leaving a small but unsightly mound of dirt at the entrance. The cell is provisioned with food such as spiders, caterpillars, cicadas and other insects that have been stung and paralyzed. The female then lays an egg on the food and seals the cell. These are not social insects, so each burrow is the result of efforts by a single female. The only real damage done by the cicada killer wasps is to lawns or flower beds, and the mental anxiety which may cause for the homeowner’s family. Female wasps will not sting unless they are handled, but their sting can be painful. Similar problems and behaviors are sometimes observed from a large black wasp of the genus Chlorion.
Certain Sphecid wasps construct their nests of mud, and are commonly known as “mud daubers”. They are frequently observed visiting the edges of mud puddles during the summer, where they obtain mud to make their nests. Their mud nests are often found plastered among the rafters of attics, garages or out buildings, or on the sides of buildings. Mud daubers typically prey on spiders. The chance of being stung by a mud dauber is rather remote, but their nests should be approached with some caution. The insect or spider prey in these nest, along with the wasp larval and pupal cast skins, can support a population of dermestid beetles such as the cabinet and carpet beetles. Some dermestid infestations of homes will originate in these wasp nest, so they should be removed and destroyed after control is achieved.
BEES (Families Apidae, Xylocopidae, and Bombidae)
Honey Bees (Family Apida, Apis mellifera) – The most serious problems results when a swarm of wild bees locates a small opening or openings in an exterior wall, chimney, or behind some faulty flashing of a home, and then nests in a wall void or some other interior area.
Honeybees may be various shades of yellow, black brown, or orange; with the head, antennae, legs and a portion of the abdomen being dark. The body is covered with light-colored hairs, thickest on top of the thorax. Worker bees are usually about 2/3 inch long. This is a social species with three adult castes: queens (only one lays eggs in each colony), drones (males), and workers (sterile females). Individual colonies may have 20-50,000 bees.
Social behavior is highly evolved in the honeybee. In addition to feeding the larvae, workers also amass reserve supplies of home which can be utilized as food by all members of the colony during periods of adverse conditions.
Honeybee nests are made of many wax cells which the workers construct. As with yellowjackets and nests of other social wasps discussed previously, these masses of cells are called combs. However, while some of these cells are used to house the immature stages (eggs, larvae, and pupae), others serve as a storage site for honey. If honey bees become well established within the wall voids of a house, large amounts of wax and honey may collect within the wall. As long as the bees are active, the workers keep the air moving inside the nest by fanning with their wings so the temperature remains below the melting point of the wax. If the bees are killed, this form of air conditioning ceases to function. In warm weather, wax within the wall void may become soft enough to melt. The honey then seeps out of the storage cells, creating a mess. If there is a sufficient amount of honey inside the walls, enough may be absorbed by plaster of similar porous wall material that an unsightly and virtually permanent stain may appear on the inside wall.
Carpenter bees (Xylocopa spp.) – Carpenter bees resembles largeCarpenter Bee bumblebees, but have very different nesting behavior. They bore long tunnels into wood and divide these tunnels into cells where individual larvae will develop. The common eastern species, Xylocopa virginica, resembles many of the bumblebees closely enough that they are often confused on casual observation. This carpenter bee is black in color and marked with areas of yellowish hair, but the dorsal side of the abdominal segments (except for the apparent first segment) have no areas of yellow hair. Other species of carpenter bees may be black, green, or somewhat purplish in color, and are variously marked with whitish, yellowish or reddish hair. The dorsal surface of the abdomen is generally bare in these species also.
The typical carpenter bee gallery has an entrance hole on the wood surface. The gallery continues inward for a short distance, then turns sharply upward and runs in the same direction of the grain of the wood. The female provisions the galleries by inserting a ball of pollen upon which the egg is laid. The female then closes the cell by placing a mass of wood pulp in the gallery. As series of cells are made as the bee works backwards, out to the gallery. Females often enlarge existing galleries or use old ones, so very complex gallery systems are often made into the siding or window trim of homes, and in such cases the structural strength of tunneled timbers may be reduced.
Carpenter bee nests are usually not difficult to locate. Some of the more common sites chosen within buildings include siding, eaves, wooden shakes, porch ceilings, window sills, doors, and so forth. Unpainted or well-weathered wood is much more susceptible to attack than hardwood or well-painted timbers.
Carpenter bees complete one generation per year in most areas of the United States. Tunnels are prepared and eggs laid in the spring. Larvae and pupae develop in the closed cells in early summer. Adult bees emerge in late summer and return to the same tunnels to hibernate for the winter months. In the spring, the adults mate and lay eggs, completing the cycle.
Bumble Bees (Family Bombidae – Bombus spp.) Bumblebees areBumble Bee social insects which generally nest underground. They do not make holes in tunnels in wood, but will nest in abandoned mouse burrows under piles of grass clippings or leaves, stones, logs or other such locations. They seldom become a problem of consequence except in situations where the nest are established close to a sidewalk, near a building foundation, or in some other location where conflict with people or pets is inevitable. There are a number of species which may be rather commonly encountered, some of which are more likely to sting people than others. Whenever the nest area is directly threatened, bumble bees will attack and sting the intruder as a defensive reaction.