October 2011: The Circle of Life: The good, the bad, and the "doesn't much matter" facts about butterflies, moths and caterpillars.

The stinging caterpillars weren’t very bad this year. There probably isn’t any absolute answer to why they are so numerous one year and not the next.

Abe Oliver, one of our entomology friends, said that he thinks some kind of virus kicks in when the caterpillar population gets very high and most of them die off. He was probably right to some degree but this matter of good and bad insect years is complicated.

We will start by describing the life cycle of the stinging caterpillar—and promise not to bother you with any more “cycles.” All caterpillars are the larval stage of some kind of butterfly or moth. The pretty ones are called butterflies and they fly around during the day; moths are sort of drab looking and fly at night. The stinging caterpillar is a buck moth larva. The mamas and papas emerge from the ground in September or October and fly around, just to “party.” They don’t eat anything because they have no mouth parts. After mating, the female lays eggs near the stem tip of an oak tree, and dies. When the tree begins to produce new, tender, leaves in the spring, the eggs hatch and stay in little clusters, nibbling on leaves, until they get large enough to crawl around alone and continue to eat leaves. Ultimately, they get big and fat and crawl or fall from the tree. By this time they have developed those spines that will sting any bird that is looking for a meal, or any human foolish enough to touch them. When you touch one, those spines stick into you and hurt—boy do they hurt! You can remove the spines with adhesive tape, and baking soda will help to reduce the pain, but you will remember not to do that again. After crawling around for a day or two (we don’t know how long) they burrow into the ground or leaf debris and pupate. Then in September or October the moths emerge and the cycle is over.

We went into these details partly to show that there isn’t much you can do to control those caterpillars. Some people spread aluminum foil around the base of the tree because some of the caterpillars crawl back up into the tree, but not to lay eggs. The moths do that. If you were to see the tiny caterpillars just after they hatch you could hire someone to spray the entire tree but that is expensive and would help only if you had one oak tree. Stinging caterpillars are numerous some years and not in others. There seems to be no cycle, disease may play a part and it may be due largely to climate. Maybe the oak leaves started growing, the eggs hatched, and there was a cold snap. Nobody seems to know.

Having mentioned butterflies, we will do a short report on them. All moth-like insects follow the same general cycle: eggs, larvae, pupae, and adults. The caterpillars of butterflies are small and they don’t eat much before pupating, but the butterflies do have mouthparts and get food energy from nectar of flowers, but also from rotten fruit and decaying animals! It is more interesting to think of butterflies feeding in butterfly gardens, but they need more nutrients than they can get from sweet nectar. They also drink muddy water to get some necessary salts. Most butterflies are beautiful, feed on flowers and do very little harm to plants.

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