ANTS, BEES, AND WASPS (HYMENOPTERA) are part of a diverse order of insects that includes groups that are of great importance to soil life as movers of soil, predators and parasitoids. Ants bees, predatory wasps and parasitoid wasps have narrow, waist-like constrictions; two pairs of membranous wings; and long, threadlike antennae.
Ants
PHYLUM: Arthropoda » CLASS: Insecta » ORDER: Hymenoptera » FAMILY: Formicidae
SIZE: 0.04–0.98" (1–25 mm).
ECOLOGICAL ROLE: Ants are among the most significant insect groups in soil. They move a great deal of soil and influence soil structure, and they are predators of small invertebrates. Ants are also important seed dispersers.
DESCRIPTION: Ants are red, brown or black. Between their thorax and abdomen, they have a constricted waist with one or two upright lobes. Their antennae are elbowed (the first segment is very long). Queens are larger than workers and have wings, though they shed these after mating. Males are winged and are much smaller than queens.
WHERE THEY ARE FOUND: Ant colonies can be on the soil surface in leaf litter or dead wood, with a few species nesting inside trees, but the majority of ants in North America nest underground. Ants construct extensive nests with chambers and tunnels and excavate quite a lot of soil, adding a great variety of organic matter. Ants occur in all terrestrial habitats—they are found as far and wide as the Arctic and oceanic islands.
WHAT THEY EAT: Many species are carnivorous on small arthropods or are scavengers of dead animals; others feed on plants, sap, nectar or honeydew, and some eat fungi.
LIFE CYCLE: All ant species are truly social insects. They live in complex colonies, nesting with a queen who reproduces, workers who perform specific roles (e.g., guard, forage, or nurse), and overlapping generations. Males and queens are produced in large numbers at one time of the year; they then emerge from colonies and mate, and males die quickly after. The mated queen locates a suitable nesting site and produces her brood; once workers emerge, they take over care of the colony. Colonies are perennial and may persist for several years. Colonies vary in size from 12 to thousands and can be complex in structure and organization. Ants secrete substances that act as odor trails or alarms to stimulate activity.
APPROX. NUMBER OF KNOWN SPECIES: 14,000 worldwide (700 in North America).
RELATIVE ABUNDANCE: Ants are among the most abundant insects in the world and outnumber most other terrestrial animals; about 1% of all insect individuals are ants.
NOTES OF INTEREST:
- Ants occur on all continents except Antarctica, and their diversity is highest in tropical areas. The biomass of ants in rainforests is equal to or greater than the biomass of all vertebrates in the rainforest combined.
- Some ants have a stinger (a modified ovipositor) but some have lost the stinger and spray formic acid in defense. All ants may bite.
- Some ants have a symbiotic relationship with aphids, protecting them from harm or transporting them between plants and, in return, feeding on the honeydew (the sugary secretions) the aphids provide.
- Harvester ants (Pogonomyrmex spp.) in the U.S. desert Southwest carry approximately 15 million seeds per acre per year, which is about 1% of the total seed crop.
- Some seeds have fleshy structures, called elaiosomes, which entice ants to carry the seeds long distances. Ants will consume the elaiosomes, which contain lots of nutrients.
- There are more than 40 introduced species of ants in the United States, and some are major pests on farms (e.g., red imported fire ants aggressively defend their nests) while others are pests in cities (e.g., Argentine ants invade homes looking for food).
- In the southwestern United States, harvester ant galleries can be as deep as 15' (4.6 m) underground. Workers of another desert ant move 150–300 lb. (68– 16 kg) of subsoil to the surface for every anthill they construct!
- Ants in a Massachusetts field moved enough soil in one year to cover the field with a 0.19" (5 mm) layer, adding up to 30 tons per acre.
- Rove, hister, feather-winged and short-winged mold beetles may all be found in ant colonies, as well as mites, cockroaches and bristletails. These visitors are referred to as inquilines, and benefit from living in close proximity to the ants without causing them harm.
- In the eastern United States, mound-building ants (Formica spp.) create earthworks of 2–3' (0.61–0.91 m) in diameter and often as high.
- Tillage can reduce ant numbers and ant predation on crop pests.
Scarab-hunting wasps
PHYLUM: Arthropoda » CLASS: Insecta » ORDER: Hymenoptera » FAMILIES: Scoliidae, Tiphiidae
SIZE: Scoliid wasps: 0.79–2" (20–50 mm); Tiphiid wasps: 0.24–0.98" (6–25 mm).
ECOLOGICAL ROLE: Scarab-hunting wasps are external parasitoids, helping to control scarab beetle populations, and also move earth as they dig to find their hosts.
DESCRIPTION: There are two main groups of scarab-hunting wasps: scoliid wasps and tiphiid wasps. Adult scoliid wasps are large, robust wasps that have spiny, bristly legs. Their bodies are often black with bright orange, yellow or red colorations, and their wings are darkened or metallic blue-black. Tiphiid wasps have slender bodies and elongated abdomens. Most tiphiid wasps are black, though some also have yellow markings. Females of some tiphiid species may be wingless.
WHERE THEY ARE FOUND: Scarab-hunting wasp larvae are found in the soil, developing on their beetle hosts. Adults are found on flowers or searching grassy areas for beetle grubs.
WHAT THEY EAT: These wasp larvae are parasitoids of beetle larvae, particularly scarab beetles, including Japanese beetles. The adult female wasps search fields and lawns for beetle grubs, and when they detect them, dig down through the soil to the grub, para it, lay an egg on it, and leave the grub for their Sometimes these wasps will paralyze grubs without leaving eggs, and grubs do not recover from the sting. Adults consume nectar.
LIFE CYCLE: Scarab-hunting wasps lay eggs next to their beetle hosts, and larvae develop on hosts. Pupae overwinter in soil. Ten to 12 months pass between egg deposition and emergence of adults, and there is one generation per year.
APPROX. NUMBER OF KNOWN SPECIES: 560 scoliid wasps worldwide (20 in North America) and 1,500 tiphiid wasps worldwide (200 in North America).
RELATIVE ABUNDANCE: Data unavailable.
NOTES OF INTEREST:
- Incorporating nectar-producing flowers into the landscape can increase these wasps’ parasitism of beetle grubs.
Ground-nesting bees
PHYLUM: Arthropoda » CLASS: Insecta » ORDER: Hymenoptera » FAMILIES: Andrenidae, Apidae, Colletidae, Halictidae, Melittidae
SIZE: 0.16–0.79" (4–20 mm).
ECOLOGICAL ROLE: Ground-nesting bees are critically important pollinators of wild plants and many crops. These bees are diggers, moving and aerating soil as they construct nests in which their young will develop. Some nests are shallow—only a few centimeters deep—while others may be a 3.3' (1 m) or more deep.
DESCRIPTION: Ground-nesting bees have two pairs of wings, threadlike antennae longer than their head, and a constricted waist that connects their thorax and abdomen. Body color may be dark, metallic gold, green or blue, sometimes with stripes on the abdomen. Some species are very hairy, and females have long hairs on their hind legs and thorax, modified for carrying large quantities of pollen.
WHERE THEY ARE FOUND: Bees can be found on flowers, including wildflowers and blooms of flowering shrubs and trees. Ground-nesting bees construct nests in soils of their preference. Many prefer sandy or loamy soils, but some will nest in clayey soils. Some have very specific soil preferences—the alkali bee (Nomia melanderi), for example, nests in subirrigated alkaline soil. Different species also have preferences regarding nest depth and architecture.
WHAT THEY EAT: Ground-nesting bee larvae consume provisions of pollen and nectar within the nest. Adults drink nectar from flowers.
LIFE CYCLE: These bees lay eggs within a chamber that’s filled with food supplies and located in a subterranean nest. Larvae consume their provisions quickly and enter a resting phase as a prepupae or pupae. Some species have a single generation per year, while others have several. Those species that have one generation are only on the wing as adults for three to six weeks, emerging during a particular season. Bees that specialize on the pollen of certain plant species will time their emergence with the flowering of the plant.
Most species are solitary, and the female constructs her nest and collects provisions for her young alone. Some species form semi-social colonies where they live cooperatively with their sisters, and others form primitively social colonies with some division of labor.
APPROX. NUMBER OF KNOWN SPECIES:15,000 worldwide (2,900 in the United States).
RELATIVE ABUNDANCE: Some bees can nest in huge aggregations with thousands of individuals sharing a good nest site. When this happens, there may be two or three dozen nests per square foot.
NOTES OF INTEREST:
- Some species visit a wide range of flowers to collect pollen, while others only collect pollen from a small subset of flowering plants.
- Most bees are solitary and are very docile, avoiding defense of their nest. The name “tickle bee” was coined by students at a Portland, Oregon, elementary school where tens of thousands of mining bees nest in their playing field. The children would catch the bees during recess and said they tickled in their hands.
- The nests of cellophane bees (Colletes spp.) are lined with a distinctive cellophane-like substance to protect their growing offspring from water and mold. The cell lining, made from saliva and a secretion from a gland on the bee’s abdomen, makes the cells waterproof, and these bees often nest near creeks.
- Male bees do not have a nest to return to at night and will sleep on plants, often in clusters, clamping their jaws around the stem and resting until morning.
- Sweat bees, in the family Halictidae, will lick sweat from human skin to obtain salt.
- Reducing tillage can support ground-nesting bees, as can on-farm flowering plant habitat. Beware that tillage that reaches a depth of 6–12" (15.2–30.5 cm) may destroy part or all of some bee nests.
- A few bees in the family Megachilidae will create shallow nests in the soil and use plant materials such as leaves or resins in their nest construction.
Bumble bees
PHYLUM: Arthropoda » CLASS: Insecta » ORDER: Hymenoptera » FAMILY: Apidae » GENUS: Bombus
SIZE: 0.39–1.06" (10–27 mm).
ECOLOGICAL ROLE: Bumble bee queens move soil when they dig burrows for overwintering, as well as occasionally in the construction of their nests. Bumble bees are critically important pollinators of crops and wild trees, shrubs and wildflowers.
DESCRIPTION: Bumble bees are robust and have extremely hairy or fuzzy black-and-yellow bodies, sometimes with additional orange, red, white or brown. They have long antennae and membranous wings.
WHERE THEY ARE FOUND: Queens select an existing insulated cavity in or above the ground. Nest sites include old rodent burrows or cavities beneath a clump of bunch grass. In the winter, queens hibernate in shallow underground burrows, often under forest humus, at the base of shrubs, or in rock or brush piles. Adults visit the flowers of a vast range of wildflowers, shrubs, and trees.
WHAT THEY EAT: Larvae consume a mix of pollen and nectar, and adults drink nectar.
LIFE CYCLE: Bumble bees are social insects that live in colonies of 25 to 400, founded by a queen. Mated queen bumble bees hibernate through winter, initiate a nest in early spring, and then forage widely to provision that nest. Worker bees, the daughters of the queen, help in nest building, brood rearing, and defense of the nest as the colony grows in size through spring and summer. In late summer and autumn, new queens and males are reared and leave their nests to find mates. Males, workers, and old queens will die when winter arrives.
APPROX. NUMBER OF KNOWN SPECIES: 260 worldwide (46 in North America).
RELATIVE ABUNDANCE: Data unavailable.
NOTES OF INTEREST:
- Bumble bees are critically important pollinators of wild plants and many blooming crops.
- Bumble bees can generate internal body heat by shivering their flight muscles, which allows them to be active in cooler weather. As a group, they are more diverse in cooler climates or at high altitudes than in warmer climates.
- An older name for these bees is humble bees, because of the humming noise they make while flying. And, for Harry Potter fans, dumbledore is an 18th-century word for bumble bee.
- Not all bumble bees make a nest: several species are nest parasites of other Bombus species.
- Permanent habitat on farms can support bumble bees.
Ground-nesting predatory wasps
PHYLUM: Arthropoda » CLASS: Insecta » ORDER: Hymenoptera » FAMILIES: Sphecidae, Vespidae
SIZE: 0.39–1.2" (10–30 mm).
ECOLOGICAL ROLE: Ground-nesting predatory wasps fit into soil food webs and aboveground food webs as predators of soil animals and as pollinators of some flowering plants. Those that build nests in the ground also move and mix soils. Predatory wasps are important in agricultural systems, as they contribute to the control of some crop pests.
DESCRIPTION: Adult wasps in the family Vespidae have a notch along the inner margin of their eyes, a thin waist, and are black or brown with white, yellow, red, or orange markings. Vespid wasps fold their wings in half when at rest (they appear to have only one thin pair of wings). Adults in the family Sphecidae have a very thin, elongated waist, and are fully black, slightly metallic, or black with red, yellow, or white markings. Sphecid wasps tend to be slenderer than vespid wasps and do not have notched eyes.
WHERE THEY ARE FOUND: Many ground-nesting predatory wasp species construct underground nests, in which their young develop. Some species also construct nests out of clay or inside stems or cavities above ground. All sphecid wasps and most vespid wasps are solitary, with each individual female constructing and provisioning her nest; these wasps do not defend their nests. Yellowjackets (Vespula spp.) are social, forming colonies with a queen and dividing labor among female workers; these wasps can be aggressive in defending their nests, which are built inside existing burrows in the ground. Adults are found on flowers or searching for prey on the soil, in leaf litter, or on vegetation.
WHAT THEY EAT: Adult females collect prey to bring back to their nests as food for their carnivorous larvae. Some species are generalists, feeding on a variety of insects, and others may hunt more selectively on particular pest groups such as grasshoppers, caterpillars, or aphids. Adult wasps feed primarily on nectar, although some species also feed on rotting fruit or the juices of prey.
LIFE CYCLE: Ground-nesting predatory wasps lay eggs in a chamber within a nest, adding prey as a food source. Some species have only one generation a year, while others have multiple.
APPROX. NUMBER OF KNOWN SPECIES: 5,000 Vespidae worldwide (320 in North America) and 800 Sphecidae worldwide (125 in North America).
RELATIVE ABUNDANCE: Data unavailable.
NOTES OF INTEREST:
- Sphecid wasps stock the nest with whole, paralyzed prey. Vespid wasps chew their prey to a pulp before taking it to the nest.
- Sand wasps (Bycertes and Bembix) nest in sandy soils, and mothers continuously bring food to their growing larvae. One larval sand wasp can eat as many as 30 stink bugs.
- Cicada killer wasps (Sphecius) are large, striking wasps with black and yellow coloration. Female wasps paralyze cicadas, which they then carry back to their underground burrows. Sometimes you can see the wasps carry the cicada partway up a tree to gain altitude before flying back to their nest with their heavy load.
- Flowering plant habitat can support adults as well as their contributions to conservation biocontrol.
Velvet ants
PHYLUM: Arthropoda » CLASS: Insecta » ORDER: Hymenoptera » FAMILY: Mutillidae
SIZE: 0.23–1.2" (6 mm–3 cm).
ECOLOGICAL ROLE: Velvet ants, a group of wasps, are external parasitoids on some soil insects, feeding on and killing their hosts.
DESCRIPTION: These wasps have skinny waists and resemble ants, but they are very hairy and usually brightly colored with orange, red, yellow or black hairs. Females are wingless and have stingers, while males have wings and are stingless.
WHERE THEY ARE FOUND: Larvae are underground with their hosts. Adult females can be seen on the soil surface, and males are sometimes found on flowers.
WHAT THEY EAT: These wasps primarily parasitize ground-nesting bees and wasps but may also attack a few other soil-dwelling insects. Adults eat nectar.
LIFE CYCLE: Female velvet ants dig through soil or break into mud nests to find their hosts. Then, velvet ants lay eggs on the surface of their host’s body. Larvae hatch and consume their hosts (which are usually in the larval stage) within a few days. Larvae then spin cocoons and pupate; most species overwinter as pupa. Velvet ants have one generation a year.
APPROX. NUMBER OF KNOWN SPECIES: 8,000 worldwide (483 in North America).
RELATIVE ABUNDANCE: Data unavailable.
NOTES OF INTEREST:
- Females are sometimes called cow killers because of their powerful stings, which have been reported to be among the most painful of insect stings.
- Females also have extra hard exoskeletons to help ward off the defense attempts of hosts.
- Velvet ants squeak to deter predators.
Parasitoid wasps
PHYLUM: Arthropoda » CLASS: Insecta » ORDER: Hymenoptera » SUPERFAMILIES: Chalcidoidea*, Ichneumonoidea*
* There are additional parasitoid wasp superfamilies, but these two contain by far most of the species of internal parasitoids.
SIZE: 0.06–0.8" (1–20 mm).
ECOLOGICAL ROLE: These wasps are internal parasitoids of soil arthropods, living on and killing their hosts. There are also many species that live aboveground that are important in agricultural systems, contributing to the control of crop pests.
DESCRIPTION: As adult wasps, some species are extremely tiny while others are more sizable. Although this may be hard to see, these wasps all have slender bodies with narrow waists. Many parasitoids of soil insects have no wings. Females have an ovipositor, a long, stinger-like appendage used to deposit eggs into hosts, though it is less visible in some species.
WHERE THEY ARE FOUND: Larvae live within their hosts. Adults can be found on flowers with shallow nectar reserves.
WHAT THEY EAT: Many parasitoid wasps are host specific and are highly effective in regulating the populations of certain pests. Hosts include eggs, larvae or adults of soil insects (and many other insects, including parasitoid wasps themselves). The life cycle of parasitoid wasps is closely synchronized to that of their hosts. An adult female wasp finds a host at the appropriate life stage and deposits one or several eggs on, inside, or near the host. The larvae develop on or inside the host, feeding on it, but usually not killing the host until the wasp larvae reach maturity and pupate. Adult wasps emerge and seek new hosts to repeat the cycle.
LIFE CYCLE: Parasitoid wasps lay eggs on the surface of or inserted inside a host’s body. These wasps overwinter as an egg or larva within their host, as a pupa within their cocoon, or as adults.
APPROX. NUMBER OF KNOWN SPECIES: 42,000 in the superfamily Ichneumonoidea worldwide (5,000 in North America) and 22,000 in the superfamily Chalcidoidea worldwide (2,600 in North America). Estimates for both superfamilies are significantly higher (500,000 species worldwide), but most remain undescribed.
RELATIVE ABUNDANCE: Data unavailable.
NOTES OF INTEREST:
- These wasps need habitat that provides nectar sources for adults, as well as habitat for their hosts.
- Species diversity of parasitoid wasps is extremely high. Parasitoid wasps probably have more species than any other insect group. An estimated 15% of all insects are parasitic on other arthropods. There are even parasitoid wasps that parasitize other parasitoid wasps; these are known as hyperparasitoids.
This material is based upon work that is supported by the National Institute of Food and Agriculture, U.S. Department of Agriculture through the Sustainable Agriculture Research and Education (SARE) program. Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the view of the U.S. Department of Agriculture or SARE.