Friday, July 20, 2007

Article: A home for termites

Reproductive flight of subterranean termites

A couple of weeks ago I was outside standing in a light drizzle waiting for the vet to come look at one of my horses. Due to the overabundance of rain this year, insect populations have thrived. This fact asserted itself on me most obviously through the tiny gnats that persisted in landing on and walking across every inch of my exposed skin. More annoying than even the gnats, the constant buzz of mosquitoes and their too-frequent bites kept me busy swatting the air.

The vet took forever to arrive. I had nothing to do but stare down the drive looking for her. As I did, I noticed that there were a lot of flying insects mixed in with the raindrops. Small and colorless, I assumed they were moths and paid little attention to them. It wasn’t until my daughter Coral pointed out that they were coming out of a hole in the ground that I took an interest. I went to see what was going on.

Rising from a hole amid the caliche of the driveway, emerged a constant stream of winged insects. Each new arrival took to the air as soon as it was clear of the hole. Around them bustled smaller, whitish, wingless insects. I bent down to get a closer look. I hadn’t recognized the winged alates but I immediately knew the others to be some of the most destructive insects in the world: subterranean termites. As I watched hundreds of them were taking their nuptial flights, seeking to start their own colonies.

Termites are fascinating creatures. They are the only fully social insects that are not in the hymenoptera, the order containing wasps, bees and ants. Termites belong to their own order, the isoptera. They are most closely related to cockroaches. In fact, some roaches eat wood in the same way termites do. Uniquely, termites and the aforementioned roaches, have intestinal symbiotes to digest cellulose.

Like all insects, termites have to shed their exoskeleton in order to molt. The exoskeleton actually includes the lining of the gut and so when termites shed, they lose all of their intestinal contents, including the flagellates without which they cannot live. For this reason every termite larva and every adult after molting must be re-inoculated with the correct intestinal flora. Termites do this by anal feeding. It is thought that this dependence may have the impetus that drove termites down the path to social behavior.

As I watched the seemingly endless stream of reproductives helped out of their nest by soldiers and workers, I was reminded that most termites are completely blind, only the queens and kings even have eyes. In their mounds, termites live in constant darkness and they never forage in the open. This behavior allows termite infestations in houses to persist for long periods before they are noticed.

Looking around I could see that plenty of potential for new colonies to start on or around our house. In fact, the colony that I was observing apparently lay under the driveway, the one place on our property where the availability of cellulose seems limited.

On the other hand, we also have hundreds of trees, especially along the banks of Garlic Creek which passes just in front of the house. These trees are constantly shedding small branches and leaves and the creek imports significant driftwood from upstream when it rains. Nature has a way of taking care of that stuff so that I don’t have to and that is termites. In addition, termites are a valuable food source to many birds including a family of woodpeckers that I’ve enjoyed observing this summer.

Like everything, termites have good and bad aspects when viewed from a human perspective. I guess I’m going to have to have the house inspected because the termites cannot be allowed to feed on it. On the other hand, termites are part of the natural environment and watching their nuptial flight was a unique experience and a glimpse into their nearly invisible lives. As long as they know their place, I think we can get along.

For more information:
The Insect Societies by E.O. Wilson, Harvard University Press
Dr. Don’s Termite Pages:

Photo: Note that the workers are eyeless while the winged form has prominent eyes
Photo: Termite workers and soldiers aid a alate emerging from the ground
Photo: Ladderback woodpeckers looking for wood-eating insects including termites

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