JUNE
2009

 

By
Tom Turpin
 
Professor of
Entomology
Purdue University

 

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Check out these books by Tom Turpin:

Flies in the face of fashion

What's Buggin You Now?

 

 

 

06-11-09

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"Dead Wood Gang" of the Insect World


Mention "Dead Wood Gang" and many people will probably visualize some band of cowboy desperados suitable for a John Wayne movie. Other folks might be reminded of people who do not carry their load in the workplace. To entomologists, though, the term would be appropriate for a group of insects that feed on dead wood.

Zoologists sometimes classify animals according to the type of food that the animal eats. The simplest of such schemes places animals in one of three groups -- plant eaters, animal eaters or dead-stuff eaters. Technically, the plant feeders are herbivores, the animal eaters are carnivores and the dead-stuff eaters are saprophytes.

Insect saprophytes include various species of fly maggots that consume the flesh of dead animals, animal manure or rotting vegetation. Also included are dung beetles that feed on mammal manure and burying beetles that feast on dead animals. In general, we humans don't mind having insect saprophytes getting rid of dead stuff. Just part of the ecology of the earth, nature's way of recycling, we say.

Wood-eating insects are also valuable recyclers in nature. These insects consume and digest wood and, as a result, recycle nutrients into the forest ecosystem. Without the activity of wood-eating insects, dead trees would rot very, very slowly and replacement trees would grow more slowly due to a reduced nutrient supply.

However, insects don't distinguish between dead trees in the forest and wood used to make things like houses and furniture. So when saprophytic insects ply their ecological trade on some of our wooden possessions, we cry foul and brand the perpetrator and the deed dastardly. The insect culprit then gets saddled with the label of pest.

So which insects are the despicable desperados of the deadwood gang? Those brazen enough to try to recycle "our" wood certainly qualify. The first that comes to mind are termites. There are some 3,000 species of termites in the world. All termites are social insects that live in a colony of thousands of individuals ruled by a queen.

The nests of many termite species are located in the soil. It is from this nest site that the termites launch their search for food, generally wood. Once wood is found, the termites chew it up and swallow it into their gut, where protozoa or bacteria aid in the digestion of the cellulose.

Termites are the most important wood-damaging insects in the world. The cost for preventing and repairing termite damage in the United States is estimated to exceed $3 billion annually.

Long-horned beetles are also part of the dead wood gang of insects. These insects get their name because their long antennae often exceed the length of the insect's body. Unlike termites that seldom attack living trees, the long-horned beetles include a number of species that attack and kill specific trees. The emerald ash borers and Asian long-horned beetles are examples.

It is the larvae of the long-horned beetles that feed on trees and in doing so leave tell tale tunnels in the wood. Many species feed only on freshly fallen trees and therefore are an important contributor to the onset of decay. The extensive tunneling and sawdust-like manure left by the feeding larvae suggest the name sawyer, a term applied to saw-wielding woodcutters, for one species of this group of insects.

A small insect that shows up in dead wood is known very descriptively as the powder-post beetle. This beetle's name is based on production of fine powder as it bores in dry wood, such as furniture, floors, tool handles and beams of log cabins.

Carpenter ants, as their name suggests, are also associated with dead wood. These ants do not feed on the wood, but they do build their nests in dead and rotting wood. Carpenter ants will also build nests in the structure of buildings, especially where adequate moisture is present.

Another insect carpenter, the carpenter bee, will bore holes in wood to construct nest cavities. Like carpenter ants, carpenter bees chew, but do not consume, wood to fashion a nest cavity.

Even some of our worst insect pests have a good side, including those that feed on wood. In addition to being nutrient recyclers, these insects can become food for other animals. That's the reason that the insects of the dead wood gang shudder when the woodpecker posse comes to town.

 

Writer: Tom Turpin
Editor: Olivia Maddox