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Insect orders are not of the marching type
On Six Legs
By Tom Turpin

One area of study of importance to biologists is called “classification.” Biological classification is, by definition, a systematic arrangement of plants and animals in groups based upon some definite scheme. The common categories in such a scheme for animals are phylum, class, order, family, genus, species and variety.

In such a classification scheme, insects belong to the phylum Arthropoda. Arthropods are defined as joint-footed creatures. Things with jointed feet and legs, in addition to insects, are spiders, millipedes, centipedes, ticks, mites, crayfish, lobsters, shrimp and sowbugs.

The next lower category in this scheme is class. There are several classes of arthropods. Insects belong to the class Insecta. Spiders, ticks, and mites are in the class Arachnida. The class Crustacea includes the crayfish, shrimp, lobsters and sowbugs. Centipedes are in the class Chilopoda and millipedes in the class Diplopoda. Like all classes of animals, the class Insecta is divided into orders.

Historically, order names of Insecta were based on structural characteristics of the insect, primarily the wings and mouthparts. In 1954, a popular entomology textbook, the second edition “An Introduction to the Study of Insects” by Borror and DeLong, listed 26 insect orders. At that time, not all scientists grouped the insects into 26 orders. Some had more orders, others less, according to their system.

Ideas relative to any scientific matter can change based on new information becoming available. For example, modern molecular biology techniques have allowed scientists to look at the DNA structure of insects. Such information might suggest different groupings of insects within classification categories.

In 1989, the sixth edition of “An Introduction to the Study of Insects” places insects in the class Hexapoda. Within that class are 31 orders. The increase in number of orders resulted when some orders were separated into independent groups. The order Orthoptera in the second edition included walking sticks, praying mantids, katydids, grasshoppers, crickets and cockroaches. In the sixth edition, the order Orthoptera remained, and it included the grasshoppers, crickets and katydids. The other groups were split out into their own orders. Walking sticks were Phasmida, mantids were Mantodea and cockroaches Blattaria.

But the authors also decided to combine two orders. The order Anoplura had the sucking lice and the order Mallophaga the chewing lice. These orders were combined into Phthiraptera.

Repositioning groups in systems of classification is an ageless and ongoing process in science. The obvious result of this is more or less groups than before. Consequently, people who do this work have generally come to be known as either “lumpers” or “splitters.”

Lumpers combine groups. Splitters divide groups. All of this regrouping within classification schemes can be a bit confusing to the general public and to scientists. But then, science is always changing. Otherwise it would be history.

So what are some of the common insect orders? One of the most visible is Lepidoptera, which includes the butterflies and moths. This order name, like many insect order names, ends in “ptera,” which is Greek for “wing.” So the Lepidoptera are the scale-winged insects. Coleoptera includes the beetles that literally are the sheath-winged insects. The sheath refers to the hard shell-like front wing or elytra. The flies are Diptera or two-winged insects and bees and wasps, Hymenoptera, or membrane-winged insects. And so it goes for another 22 to 27 names, depending on which system of classification you use.

The next time you spy a butterfly fluttering about you might say something like, “Wow, did you see that beautiful day-flying Lepidopteran?” I guarantee your friends will be impressed with your knowledge of insect orders! And maybe a bit jealous of your use of scientific words.

This farm news was published in the April 12, 2006 issue of Farm World.

4/12/2006