MAY
2001

 

 

 

By
Tom Turpin
 
Professor of
Entomology
Purdue University

 

 

 

 

 

05-10-01

Bounteous Beetles Shun Limelight

In nature's scheme of things, beetles are a great success story. This probably comes as no surprise to the homeowner who wages the annual battle with overwintering ladybird beetles, or to the gardener engaged in hand-to-tarsal combat with hoards of Japanese beetles dining on roses.

Beetles are one of the most common types of animals on the surface of the Earth. It has been estimated that one in every four animal species is a beetle! Worldwide, there are more than 250 thousand species described. In North America alone, there are some 26,000 species of beetles.

In spite of these impressive numbers, most beetles go unnoticed by humans. Unlike their insect cousins the butterflies, beetles are adapted to living out of the limelight. Even their structure suggests an undercover existence.

One of the characteristics of beetles is the presence of elytra. Elytra are the hardened forewings that give beetles the look of, well, beetles. These forewings cover and protect the membranous hind wings when the beetle is not flying. When folded, the elytra meet in a straight line down the back.

That shell-like protective cover allows beetles to crawl under bark, in leaf litter or in soil without harming those delicate hind wings. But because of the heavy armor, beetles are not the most accomplished flyers.

Unlike most other flying insects, beetles have a habit of crashing into things as they fly or try to land. Witness May beetles trying to get into a house and crashing into the windowpane in the process.

The diversity of the structure of beetles is reflected in the common names of some. The lizard beetles are narrow and elongate. Horseshoe crab beetles are similar to horseshoe crabs in general appearance. Spider beetles are long-legged and resemble spiders.

Stag beetles are impressive-looking insects and get their name because males possess mandibles that are long and branched, resembling the antlers of a stag. This insect is also sometimes called a pinchingbug because it can and will bite-not the males, since the enlarged mandibles are for show, but the females with their less impressive but powerful jaws.

While the mammal unicorn did not exist outside of mythology, there is such a beetle. The unicorn beetle belongs to a group that includes some of the largest insects in the world. And the name reflects it. Along with the unicorn are rhinoceros and elephant beetles. All are from the group known as scarab beetles, most of which feed on animal dung or decomposing plant materials. It is this group that includes the sacred scarab of ancient Egypt.

While some of the beetles are among the heaviest insects in the world, the beetles also include some of the smallest. The feather-winged beetles are less than 0.5 millimeters in length. They feed in decaying wood.

There are beetles known as long-horned. The name is based on the presence of long antennae on the adults. The larvae of many of the long-horned beetles bore in wood as they feed and are known as long-horned, wood-boring beetles.

Beetles are also predators. Ladybird beetles feed on aphids and tiger beetles on any insect they can catch. The same is true of the predaceous diving beetles.

Lightning bugs are called soft-winged beetles because their elytra are more pliable than most beetles. These light-producing beetles are also predators. They feed on soft-bodied insects, slugs and snails, which is why they are commonly found in damp habitats.

There is even a beetle that is a parasite on beavers. Like most entomologists recognize, when it comes to beetles they can be found almost everywhere. What else would you expect from the most successful type of animal on Earth?  

 

Writer: Tom Turpin
Editor: Olivia Maddox