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Beetles, Beetles Everywhere

November 17, 2014
Light-colored Anomala lucicola (Photo by John Obermeyer/Purdue Entomology)

In the world of insects, beetles rule. At least they do if the number of species is an indication of success. It is widely accepted that one of every four animal species that has been a given scientific name is a beetle.

That is the reason that British biologist J.B.S. Haldane wrote in a 1940s essay, "The Creator would appear as endowed with a passion for stars, on the one hand, and for beetles on the other … ." A theologian once asked Haldane what inferences he could draw about the nature of the creator from the study of his creation. Haldane is purported to have replied, "An inordinate fondness for beetles."

It is Haldane's remark that prompted U.S. entomologist Arthur V. Evans to title his beetle book, "An Inordinate Fondness for Beetles." The beautiful photographs in Evans' book allow readers to see some of the magnificent diversity in the world of beetles.

The sheer number of beetles has prompted some biologists to declare that we live in an age of beetles. But in spite of their numbers, most of us don't notice beetles as frequently as we do some other types of insects. We see butterflies because many are big and showy. We pay attention to bees and wasps because of their potential stings and because they buzz around. And flies, well, flies just inject themselves into our lives in such a way that they are hard to miss.

What is it about beetles that have made them one of the most successful animal life forms on earth? To start with, they are insects, and insects as a group are successful organisms. One of the reasons for the success of insects is the presence of an outer skeleton that forms a tough, protective layer. This exoskeleton is covered with a wax layer to help maintain water balance. Insects also have a unique system for breathing, one that depends on passive diffusion of oxygen. Also insects are small in size, have the ability to fly and exhibit high rates of reproduction.

All of those things make insects successful animals. But why are beetles as a group the most common of the insects? So common, in fact, they are found in all types of habitats in all continents, except Antarctica. In other words, what makes a beetle different from other insects? Beetles have one of the strongest exoskeletons in the insect world. They are not easily smashed!

The front wings of beetles are modified into elytra. Elytra are rigid structures that meet in a straight line down the beetles back when the insect is not flying. The elytra protect the membranous hind wings when they are not in use. The line where elytra meet is a good way to recognize a beetle when you see one. The elytra also give beetles their scientific order name, Coleoptera. The word coleoptera literally means "sheath wing."

Most adult and baby beetles have mouthparts that are adapted for biting. While other insects can bite, the jaws are a predominate feature of most beetles. Indeed beetle jaws can be used to feed on seeds, leaves, fruits, roots, other insects, dead animals, wood and even dung. That means that beetles, both adults and young, can make use of a wide variety of food. In general, within their ranks, beetles do not have a specialized ecological niche such as bees feeding on pollen. A lack of specialization means that beetles have evolved to live in many more situations than other groups of insects.

The physical structure of beetles means that they can live in a number of habitats, often where we don't see them. To many people, the saying "out of sight, out of mind" applies to beetles. Except, of course, beetles that make pests of themselves because they feed on something we want. For instance, Japanese beetles, emerald ash borers, cucumber beetles and corn rootworm beetles, just to name a few.

On the other hand, 4-H members who are working on an insect collection frequently include a lot of beetles. I'm sure a testament to the fact that these kids, unlike most of us, are looking for insects. If we look, most of us will discover that beetles are everywhere. The most numerous of all the insects have discovered that being unobtrusive is a wonderful lifestyle!

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