3/29/04

Contacts:
Betsy Matos, Entomology, (515) 294-1999, bmatos@iastate.edu
Jean McGuire, Continuing Education and Communication Services, (515) 294-7033, jmcguire@iastate.edu

Yard and Garden Column for the Week Beginning April 2, 2004

Insects on the Moon?

By Betsy Matos
Entomology Graduate Student
Iowa State University

"Doodle-bug…doodle-bug… are you at home?" -- Astronaut Charles Duke, Apollo 16, April 16-27, 1972

Insects on the moon? Not really, but astronaut Charles Duke was definitely thinking about antlions or doodlebugs, as you may refer to them, while describing moon craters. Antlions are insects closely related to lacewings. These insects have been classified in the order Neuroptera, which literally means nerved-wings. Neuropterans are soft-bodied insects with four membranous wings which have many cross veins. These insects undergo complete metamorphosis and have an egg, larval, pupal and adult stage.

Antlions are in the largest family in the order Neuropteran, Myrmeleontidae, with approximately 2,000 species throughout the world. Approximately 80 species are found in North America, mostly in southwestern states with arid conditions.

In our home gardens, these important predators are found in the dry, sandy, loose soil. These sites could be near flower beds and under hedges or eaves. Antlion larvae build funnel shape pits, similar to craters on the moon, in which they catch their prey. The antlion larvae have sickle-shaped mandibles which are used to inject venom to subdue their prey. Antlion larvae are similar to lacewing larvae except the antlion's abdomen is broader, whereas the lacewing larvae have narrow abdomens. This broad abdomen helps the antlion build its pit with a shovel and plow action.

The antlion larvae overwinter in Iowa and are the first stage we see at the beginning of the summer. The adult resembles a damselfly; however, the antennae are longer and have a club shape tip. In addition, the adults are weak fliers than damselflies. The adults are active mostly during the night and may be attracted to porch lights and are usually present midsummer. During the day they are more difficult to find because they rest.

Some species of antlions do not hide in pits down in the soil. Instead, camouflage helps them hide from their prey. Iowa antlions are sit and wait predators, because they build the pit and wait hidden at the bottom of the pit until an ant or other prey falls. Whereas other species found throughout the world actively search for their prey.

Some entomologists say the diameter of the pit expands as the antlion grows. Antlions may become as large as a human fingernail (0.6 in) and the pits may be from 1 to 2 inches wide. Other entomologists; however, say the pit expands due to the period of time the antlion has gone without food. The bigger the pit the hungrier the antlion is, thus increasing probability of prey falling into its pit.

The prey approaches the edge of the pit, and because of the sandy properties, it may slide down the pit directly on the sickle-like mandibles. The antlions inject venom and will then suck all the contents of the prey. Antlions may go for prey that is relatively larger than their own body size. For example, some carpenter ants may be larger in body size than the antlion, but this does not stop the antlion from eating carpenter ants. After all the juicy contents have been sucked, the antlion discards the exoskeleton of the other insect or arthropod out of its pit.

An antlion may continue to be a larva for up to three years before changing into a pupal form. Antlions pupate in the soil, and the cocoon is made of silk and soil. The adult may be predaceous or feed on nectar, but its real purpose is to mate and reproduce. It may live for up to a month. Females lay eggs in sandy or loose soil areas. Hopefully, the female does not go too close to where another antlion larva may have its pit, because it may become food for the owner of the pit.

If you want to observe craters, you don't have to go to the moon. Find the nearest sandy or loose soil area around your home or in a park late in the spring or early summer. Once you have located the pits built by antlions, look for prey such as ants or other small arthropods and throw it inside the pit. The antlion will do the rest.

If you are amazed by the action of the antlions and want to take it home, don't. Antlions like other animals need to be free and make important contributions to our ecosystem. When you want to see antlions in action, just remember where you observed them previously and come back later.

Antlions are not insects commonly handled by humans and are not harmful to humans. Antlions are not pests. Overuse of insecticides near gardens and lawn will cause harm to antlions.

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ml: isugarden

Editors: Three color photos, suitable for publication, are available at right. Click on each thumbnail photo to go to the fullsized photo. The top picture's fullsize photo is 212K; the middle picture's fullsize photo is 164K; and the bottom picture's fullsize photo is 164K. Caption: AntlionPits: Antlioin pits in dry, sandy area. Photo of courtesy Greg Courtney, Department of Entomology, Iowa State University
Caption: AntlionAdult: Antlion adult. Photo courtesy of Betsy Matos, Department of Entomology, Iowa State University
Caption: AntlionLarva: Antlion larva. Photo courtesy of Betsy Matos, Department of Entomology, Iowa State University

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