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NatureSpeak Articles

Carpenter Ants: Invasion of the aliens

As I sucked them into the vacuum I couldn't deny a grudging respect for the tiny creatures that were determined to take over my cabin. Among the most successful of all living things, there are more than 9,500 described species of ants world-wide. Collectively they make up one-third the total weight of all animals on earth. And the world they inhabit is as alien to us as that on some distant galaxy: a world where chemical signals replace sight and sound.

Complex molecules, pheromones, are stored in various glands and released to communicate with other ants who pick up the messages through receptors on their antennae. Some pheromones identify members of the colony, others signal alarm, blaze trails, and even distinguish the living from the dead. The tiny brain of an ant is wired to respond to about a dozen of these chemical signals but, despite this limited perception, ants are able to form incredibly complex social organizations.

Our local cabin-raider, Camponotus pennsylvanicus or carpenter ant, is the largest North American ant. It feeds on other insects, plant juices, and the sweet honeydew secreted by aphids and scale bugs. Each fall the workers gather aphid eggs which are over-wintered in the ant's nest and "seeded" on plants the following spring. When a scout locates food, such as the jam on my kitchen counter, it blazes a scent-trail back to the nest and leads foragers back to the source.

An ant colony begins with the nuptial flight of winged virgin queens and males. If a queen successfully mates, usually with 4 or 5 males, and escapes predation she sheds her wings and selects a suitable place for a nest. The males promptly die but their sperm are stored in the spermatheca of the new queen. Alone in her nest she lays and fertilizes a few eggs and, using only the energy reserves of her own body, feeds and raises the grub-like larva into the first few workers.

At this point the colony supersedes the individual. The queen, groomed, fed, and protected by her workers is reduced to little more than an egg-laying machine; the ovaries of a superorganism in which the various worker castes (scouts, foragers, soldiers, nursery workers) become the limbs and organs. The workers themselves are all sterile females, sisters of the queen. It takes from 3 to 6 years for the new colony to reach maturity and produce its first swarm of winged reproductives. Though individual ants live less than a year the queen and hence the colony may survive for 20 or more.

Unlike termites which are able to digest the cellulose of wood, carpenter ants use wood strictly as a building material in which to excavate their elaborate galleries. Unfortunately they don't distinguish between stumps and studs so I had no compunction about using the vacuum. But, having won another round in the annual battle, I have no illusions about who will ultimately prevail. The ants have been building colonies for at least 80 million years. We humans are still learning how.

Upcoming Events:

May 5 - Monthly Bird Walk . Meet at the base of Lorimer Road at 7 a.m. ( please note earlier time!).

Web site of the week: You wouldn't believe how many Web sites there are on ants. Here's just one:

Written by: Jack Souther


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