NOVEMBER
1993

 

 

 

By
Tom Turpin
 
Professor of
Entomology
Purdue University

 

 

 

 

 

11-25-93

Insects Tune In With Antennae

Almost all insects have them. Aliens sometimes are depicted as possessing a pair or more. Our radios and televisions wouldn't work without them. So what do insects, aliens, and TVs have in common?

Antennae.

Without antennae, insects would appear a little less insect-like. Located between or below their eyes, antennae are major sensory organs of insects. Antennae are used to smell, touch, and in some cases, hear. Insect antennae are sometimes called feelers or horns.

Insect antennae vary widely in shape, but most consist of eleven segments. These segments might be threadlike, beadlike, or feathery. Some antennae are elbowed or clubbed. A few resemble the toothed edge of a saw blade.

Groups of insects can be distinguished from each other by the shape of their antennae. For instance, moths generally have fuzzy antennae while butterflies have smooth antennae with a knob at the end. The antennae of flies are reduced while bees and wasps, which sometimes resemble flies in body shape, have long antennae.

Even the sex of insects can sometimes be determined by the shape of their antennae. Male moths have fuzzier antennae than females of the same species. This is because many female moths produce a chemical attractant for males. The fuzzy antennae of the males are used to detect the chemical released by females. Male mosquitoes also have fuzzier antennae than the females. Male mosquitoes are attracted to the wing beat frequency of female mosquitoes. The fuzzy antennae are used to detect the flight of the females. Such a sound would no doubt be considered music to a male mosquito's ears, or rather antennae!

Crickets and katydids are sometimes called long-horned grasshoppers. This is because they have long antennae, sometimes twice the length of their bodies. The insects most people know as grasshoppers are called short horned because their antennae are short. In this case, their antennae are about half or less the length of their bodies.

Insects with long antennae exhibit a grooming behavior that includes cleaning these appendages. A cockroach, for example, will frequently run its antennae through its mouth, removing any dirt that might be clinging there.

Some wasps that are parasites of other insects use their antennae to track down their prey. One small wasp, a parasite of cockroach egg cases, can be observed using its antennae to trail a cockroach. By tapping its antennae on surfaces, it is able to pick up the scent left by a cockroach. When in pursuit of a roach, the tiny wasp resembles a beagle dog on the trail of a rabbit. The only difference is that you can't hear the wasp baying on the trail. Although, maybe we could if we had antennae that could pick up tiny insect sounds!

 

Writer: Tom Turpin
Editor: Andrea McCann