Whistler Naturalists

By: Cathy Conroy

Whistler Naturalists

Date: July 5, 2002


As a biologist and naturalist, there are a lot of critters that I am trained to know about that many people have never heard of. This week I was introduced to a new critter, for me anyway – the lackey moth. The lackey moth is inconspicuous and lives its very short adult life in quite an unremarkable way. This is probably why I had not heard of them; inconspicuous, short-lived, mobile, unremarkable, and difficult to detect. The immature lackey moth, however, everybody has heard of – it’s the tent caterpillar.


Lately you have probably noticed obvious masses of caterpillar colonies perched in the branches of deciduous trees all around Whistler and Pemberton. These are the silky homes of tent caterpillars, or the lackey moth larvae. The largest and most obvious ‘tents’ belong to a voracious leaf-eating caterpillar called the western tent caterpillar, adolescent form of the western lackey moth (Malacosoma californicum). There are several different species of tent caterpillars that live in North America. Some species, such as the forest tent caterpillar, prefer a solitary life with tiny tents for one, rather than the hubbub of a large colony like the western tent caterpillar.


Closely related to each other, both the western and forest lackey moths have similar life cycles, and they go something like this: The soon-to-be lackey moth is born along with hundreds of siblings in the late summer or early fall. At this point the ‘moth’ is just an egg; 150-350 eggs are laid by each female in brown egg masses about 2 cm long onto the branches of susceptible trees (alder, willow, cottonwood, aspen, etc.). Just before winter hits the insect egg transforms into a very small larva, or the adolescent form of the lackey moth, called a caterpillar. The larva remains inside the egg casing over the winter months. In the spring the small caterpillar hatches out of the egg along with all his/her siblings – and you can nearly hear their rallying cry ‘let the feast begin!’


Nights (and some days) are spent feasting on the luscious buffet of new leafy growth – so much so that some trees are completely denuded of their leaves. Unbelievably, this seldom kills the trees outright. The caterpillars spin silky ‘tents’ which provide shelter from predators and the elements, and this is where they spend most days. By late spring or early summer the caterpillar is full-grown. If they haven’t done so already, the caterpillars will soon leave their main ‘tent’ and move away from its hundreds of siblings. After finding an appropriate spot the caterpillar spins a white cocoon where it enters the pupa stage of its life. About two weeks later the developing insect emerges as the adult lackey moth – small, light brown, and inconspicuous.


The adult life then moves quickly – the moths emerge, the moths mate, the females lay their eggs, and within 24 hours of emerging from the confines of their cocoon, the moths die. And that’s it for the lackey moth, their brief adult life is over. No flitting happily from flower to flower, no trips south to Mexico like the monarch butterfly – if you are a lackey moth you mate, lay some eggs, and then die – all within a day. So it makes sense that few people have heard of the lackey moth, but nearly everyone knows the most obvious and visible form of their life cycle, the caterpillar called ‘tent’ caterpillars.


Unless you are a fruit grower, there is really no reason to panic if you have tent caterpillars in your yard. Tent caterpillars (i.e. lackey moths) have natural fluctuations in their numbers from year to year. They may be numerous this year, but there is no reason to worry that this is a permanent situation as next year there may be next to none. If that’s too long for you to wait, there are a number of non-toxic ways to deal with them, for example: pruning infested branches, rubbing the tents with a kerosene-soaked rag, or loosely wrapping the bottom of the tree with burlap to trap migrating caterpillars. There’s lots of information written on tent caterpillar controls – a good start is the Washington Toxics Coalition at www.watoxics.org.


So much for the mysteries of the lackey moths, they are as familiar to us as October rain and January snows – or ARE they?


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