Stop, look and marvel at the lowly caterpillar

Armen Tamzarian

Caterpillars forage through life one tree at a time. Emma Despland finds this fascinating. She wants everyone to know that there’s more to these creatures than just their fuzzy good looks.

“Forest tent caterpillars are common and we’ve all seen them, but nobody really looks at them twice,” she said. “When people do think about them, it’s how to kill them.”

Despland’s interest in the species began when she was completing her PhD at Oxford University in England. While writing her thesis on the desert locust, she began to feel a pull back to Canada. She joined the Department of Biology in 2002.

“In locusts, there is this individual change that is really important, and nobody has really looked at that in Canadian pest insects,” she said. “When I came back to Canada, I began looking at the same kinds of ideas, using the forest tent caterpillars as a local insect.”

Behaviour

Two years later, Despland is based at the Renaud Science Complex. Her research looks at the feeding patterns and social behaviour of the individual forest tent caterpillar in a group context. Her ultimate goal is to understand individual behaviour and what role a change in this behaviour plays in generating outbreaks.

Forest tent caterpillars prefer hardwoods such as aspen, oak, and maple. The moths lay the eggs in early summer but they only hatch the following spring when the quality of the leaves they feed on is higher.

If they hatch too early, there is nothing to eat and many will die. If they hatch too late, the quality of the food will not be at its prime and the caterpillars will not survive for long.

“If the timing is exactly right, then the population can explode.”

Despland believes there are cyclic and environmental factors involved in outbreaks. “When that happens, the amount of foliage they consume will cause harm to a tree, and if you get very bad defoliation for more than a year, it can lead to whole forests dying.”

Infestation

A serious case of infestation hit the Abitibi region of Northern Quebec two years ago. Swarms of forest tent caterpillars clustered on trees, causing massive devastation. According to Despland, it was nothing short of dramatic.

“If you looked at the forest in Abitibi, you would think it was winter,” she said. “All the spruce, the fir and so on were fine, but the broadleaved trees had no leaves.”

“You would go for a walk in the forest and there would be caterpillar droppings literally raining down on you because there were so many of them.”

There are many explanations behind these types of outbreaks. Trying to come up with the answers is all in a day’s work for the young professor.

“My day involves sitting in front of the computer doing background readings, designing experiments and analyzing data,” Despland said. She teaches Techniques in Ecology (BIOL450) and Invertebrate Diversity (BIOL398). “My students do the fun stuff in the lab.”

“It’s proven to be a good field. The more things we find out, the more questions we have.

“It’s exciting, because it means there is plenty to keep me busy for quite some time.”