Insects in your yard: Hymenoptera

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Our yards are literally abuzz in the summer with insects belonging to the taxonomic order Hymenoptera (hi-men-OP-terr-uh): bees, wasps, ants and sawflies, also called wood wasps. The third largest order of insects, scientists believe that hymenopterans evolved from sawfly-like insects that first appeared more than 200 million years ago during the Triassic Period. Hymenoptera is from the Greek humen for membrane and pteron for wing, which describes two of the common features of these insects.

How they benefit us
In our yards, bees pollinate our plants and produce honey for backyard beekeepers. Wasps pollinate, as well as prey on numerous pest insects. Ants clean up organic debris, turn our soil and feed on pests, such as slugs, aphids and spider mites. The tunneling habit of ants is said to aerate soil as much as earthworms do. On a broader scale, bees contribute billions of dollars annually to the U.S. Gross Domestic Product through crop pollination and production of honey and beeswax. And, wasps not only help pollinate, but they’re valuable to farmers, many of whom buy parasitic wasps from commercial insectaries for biological pest control. Last, but not least, the insects themselves are an important food source for other animals, including humans in some countries.

Hymenopterans are found everywhere in the world, except for colder altitudes and the Polar Regions (an exception is the very hardy bumblebee species, Bombus polaris, that ranges even into the Arctic.) The number of Hymenoptera species in the world varies, depending on the source. According to BugGuide.net, a community of professional and amateur entomologists, there are more than 153,000 species. The Smithsonian Institution and the Encyclopedia Britannica estimate about 115,000. Still other sources range as low as 100,000. Most sources agree that there are 17,000 to 18,000 species inhabiting the U.S..

Common characteristics
•  Two pairs of membranous (thin, often see-through) wings, although some species have wings only during mating flights (e.g., ants) or lack wings altogether. The wings have minimal veining and the forewings are larger than the hindwings.
•  The forewings and hindwings lock together with tiny hooks. In smaller species this can give the impression of being just a single pair.
• Compound eyes, usually large. A few ant and wasp species are blind.
•  Chewing mouthparts, although some have a modified lower lip that forms a tongue.
•  Females usually have an ovipositor (egg-laying organ) that’s modified to either saw, pierce or sting.
•  Life cycle: complete metamorphosis, which is a progression from an egg to a larva and then to a pupa from which they emerge as an adult.

Hymenopterans range in size from tiny, so-called “fairyflies,” about 0.008-inch-long (0.21 mm) to the 1.8-inch (45 mm) Asian Giant Hornet, Vespa mandarinia.

Those aren't headphones on this bee! Those are her compound eyes. (photo of Anthophora montana: Amber Reese, USGS Bee Inventory and Monitoring Lab; cc by 2.0)

Those aren’t headphones on this bee! Those are her compound eyes. (photo of Anthophora montana: Amber Reese, USGS Bee Inventory and Monitoring Lab; cc by 2.0)

Hymenoptera is split into two suborders
Bees, wasps and ants belong to Apocrita (uh-PAH-cree-tuh). This group is easily identified because they have an abdominal constriction that separates the abdomen from the thorax and looks like a “waist.” Many also have a stinger.

Notice this wasp's skinny "waist". (Magnus Johansson  / Flickr; cc by 2.0)

Suborder Apocrita: Notice this wasp’s skinny “waist”. (Magnus Johansson / Flickr; cc by 2.0)

The other suborder, Symphyta (sim-FI-tuh), consists of sawflies. Sawflies are related to wasps, but resemble flies because they lack the familiar, thin wasp “waist.” “Saw” comes from the females’ saw-like ovipositor, which they use to slit openings into plants where they lay their eggs. Almost all possess two “knobs” on their thorax called cenchri (singular cenchrus) — these hook to the underside of the wings and keep them in place while at rest. Most sawflies lack a stinger.

Suborder Symphyta: Sawflies don’t have a “waist.” (Gail Hampshire / Flickr; cc by 2.0)

Social structure
Most hymenopterans are solitary and live alone — mud dauber wasps, potter wasps and mason bees are some examples. Others are social, meaning they live in colonies — well-known examples are honeybees and bumblebees, as well as yellow jacket and paper wasps. All ants are social.

Bees
Look closely and you’ll see there are many kinds of bees in your yard, not just honeybees and bumblebees. There are also sweat bees, carpenter bees, mason bees and more. All bee species have hair somewhere on their body. The hair is important because it traps pollen. As bees move from flower to flower the pollen gets redistributed, which pollinates the plants. Their hair also helps us distinguish bees from wasps, which are mostly hairless. Bees also collect pollen, along with nectar, to carry back to their nests to feed their colonies.

Notice all the hair on this Eastern Carpenter Bee. All other bees are hairy, too. (Bob Peterson / Flickr ;cc by 2.0)

All bees have hair, some more conspicuously than others. This is an Eastern Carpenter Bee, Xylocopa virginica. (Bob Peterson / Flickr; cc by 2.0)

In winter, depending on the species, bee queens hibernate alone and their colonies die off or, like honeybees, entire colonies stay alive in their hives but don’t hibernate. They may even venture out on warm winter days.

Male bees don’t sting. The all-female worker bees sting, but they’re generally not aggressive, unless they think they’re under attack. When working in your garden, move about calmly, don’t swat at them and they’ll just go about their business as you go about your own.

All bees (except cuckoo bees) build nests. Nests are located in a variety of places. Some species, such as mason bees, nest in holes. Carpenter bees drill their own holes in wood to nest in. Others, like miner bees, dig holes in the ground. Honeybee hives may be found in trees, tree hollows or even walls and attics. Bumblebees may build their nests in such places as existing, abandoned holes underground, under sheds or loose siding, in woodpiles or in birdhouses.

There are 4,000 native bee species in North America. The southwestern U.S. and northern Mexico are home to the largest variety of bees in the world, with 1,000 to 1,200 species of bees “within a one hundred mile radius of Tucson,” according to the Carol Hayden Bee Research Center in Tucson. Around the world, about 25,000 species have been described so far. (Of these, only about 8 or 10 species are honeybees.)  All about honeybees

The smallest bees in the world belong to the genus Perdita. Native to the U.S. and Mexico, there are about 700 species and subspecies ranging in size from 0.08 to 0.39 inch (2.0 mm to 10.0 mm). The largest bees in the U.S. are carpenter bees, which measure 0.75 to 1.0 inches (1.9 to 2.54 cm) in length. Wallace’s Giant Bee, Megachile pluto, an Indonesian species, is considered to be the largest bee species in the world. The female has a body length up to 1.5 inches (38 mm) and a wingspan of 2.5 inches (63.5 mm).  

Wasps
Distinguish wasps from bees by their hairless (or mostly so) body and skinny “waist.” The waist, technically called a petiole, is a rather cylindrical body segment (sometimes two segments) that fits between the thorax and the abdomen.

Note this mason wasp’s skinny “waist.” Most smaller species of wasps, like this one — about 1/2-inch (13 mm) long — move about without drawing particular notice. It’s the large ones, such as paper wasps, hornets and cicada killers, that draw out attention. (Fyn Kynd Photography / Flickr; cc by 2.0)

Wasps are omnivorous. As adults, most wasps feed on nectar. However, they feed insects and spiders to their young, which are carnivorous. Some wasps are parasitic and lay their eggs in the bodies of live prey. Wasps nest in a variety of places. For example, yellow jackets commonly nest in the ground, but sometimes in wall voids and attics. Hornets build nests in bushes, on tree branches or sometimes the sides of buildings, in attics and walls. Paper wasp nests are constructed in trees, under the eaves of houses, in attics and other structures.

The smallest adult insects in the world are wasps — males of a parasitic Costa Rican species, Dicopomorpha echmepterygis. Wingless and blind, they measure no more than 0.005 inch (0.139 mm) in body length. The female, which has wings, is a smidgen larger. At the other extreme is an Asian species, the Asian Giant Hornet, Vespa mandarinia, which has a body length up to 1.75 inches (45 mm) and a wingspan of 3 inches. In North America, wasps range in size from minuscule to about 1.25 inches (0.2 to 30 mm) long.

Ants
Ants seem to be everywhere, don’t they? They live in colonies in innumerable places: underground, in wood, in trees, in mounds, in spaces under flowerpots and inside unused garden hoses. And, of course, kitchens, if they can get away with it!

Their colonies are headed by a queen or queens, which usually have wings. The ants we see out foraging for food are all-female worker ants, who lack wings. Colonies can be very long-lived and queens can live up to 30 years.

If a colony splits up (swarms), a different group of ants are produced -- both males and females, they have wings and fly away from the old colony to begin new colonies. Winged ants ready to swarm. (Andy Reago & Chrissy McClarren Flickr cc by 2.0)

If a colony splits up (swarms), a different group of ants is produced. Consisting of both males and females, they have wings and fly away from the old colony to begin new ones. (Andy Reago & Chrissy McClarren / Flickr cc by 2.0)

Most ants are carnivores that include sugary foods in their diet. They like syrup, jelly, honey, bananas and other fruits, but also vegetables, bread, chips and other foods that people eat. Pet food, too. You’ve probably noticed ants on your jelly feeders. Some ants, like carpenter ants, are particularly fond of a sweet liquid called honeydew that’s produced by aphids and scale insects. Ants eat other insects, dead or alive. Some eat spiders. Some species eat seeds, grains and mushrooms.

Carpenter ants don't eat wood. They feed on sweets, such as "honeydew," the sweet liquid produced by aphids and scale insects. If the come indoors, they feed on honey, jelly, other sweets, as well as pet food. Carpenter Ant. (photo: Richard Bartz / Wiki; cc by-sa 2.5)

Carpenter ants nest in wood, but don’t eat wood. If the come indoors, they feed on honey, jelly, other sweets, as well as pet food. (Richard Bartz / Wiki; cc by-sa 2.5)

Depending on the source, there are an estimated 10,000 to 12,500 species of ants around the world, with thousands more awaiting classification. Somewhere between 580 and 1,000 species inhabit North America. Most ants range in length from 0.07 to 0.4 (0.2 to 10 mm) inch. The smallest ants in the world are believed to be in the genus Carebara. Carebara atoma, for example, is only about .039 inches (1 mm) long. The largest ant in the world may be the female Dinoponera gigantea, which is 1.2 to 1.6 inches (3 to 4 cm) long. The largest ants in North America are probably Black Carpenter ants — workers are about 1/2 inch (1.27 cm) long and the queens are about 1 inch (2.54 cm) long.

Sawflies
Sawflies are wasps that have a broad connection between their abdomen and thorax that makes many of them resemble flies. The “saw” in their name comes from the female’s saw-like ovipositor (they don’t sting, however.) Another distinction, with a few exceptions, is that their larvae look like butterfly or moth caterpillars, while bee, wasp and ant larvae are grub-like. Sawflies don’t sting.

Sawfly females use their ovipositor to cut into plants, including trees. They deposit eggs in the holes and the hatched caterpillars of most species feed on the leaves, usually in groups. A few species feed on plant stems. Sawfly adults are carnivorous, but some species also feed on nectar and pollen.

There are about 9600 sawfly species in the world, with the majority in Eurasia and North America. The smallest adult sawflies are about 0.19 inch (3mm) long. Most species are in the 0.20 to 0.79 inch (5 to 20mm) range.

Images in photo composite at top of page, left to right: European Honeybee (Apis mellifera) by Esteban Armijo / Flickr; cc by 2.0; Figwort Sawfly (Tenthredo scrophulariae) by Nigel Jones / Flickr; cc by 2.0; Black Carpenter Ant (Camponotus pennsylvanicus) by Welcome Wildlife; Birch Sawfly (Cimbex femoratus) by Aleksey Gnilenkov / Wiki cc by 2.0

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