Caterpillars: Love ‘em or hate ‘em?

By Beth Sullivan

Pretty much any kind of wildlife intrigues me. I am not afraid of much but have a healthy respect for things that bite or sting. I am grateful we do not have venomous snakes to worry about in my area.

Tent Caterpillars are easy to spot in their web nests.

But I have to say I am getting pretty upset with caterpillars this spring! We have seen groves of trees denuded in a short time. Some trees never even had the chance to unfurl their leaves. Some never blossomed.

The Winter Moth

The first wave of problems was caused by the Winter Moth: A nondescript, smallish brown-gray moth that was noted in abundance last fall and into December, in pockets in southeastern Connecticut. They flew in clouds, caught in headlights, covered garage doors and patio windows. Then they disappeared, but not before laying millions of eggs on the bark and buds at the tips of branches of certain trees. They seemed to favor Oaks and fruit trees like Crab Apples and Cherries. Despite the bitter winter the eggs survived and as the spring enticed trees to begin their growth, the caterpillars hatched and ate into the developing buds. As leaves unfolded they were damaged and lacey. Their photosynthesis abilities were greatly diminished. The trees will suffer. The caterpillars were small, smooth and green, and while I felt helpless, I knew some birds were enjoying a spring feast. So there was a positive side to it…maybe. But if Oaks are too weak to produce acorns, other species will be impacted later. The trees that lost their blossoms will not produce fruit, so the birds dependent on the berries in the fall will be severely challenged.

When the leaves of infested trees emerged in spring, they were already damaged.

The birds being impacted are our own natives; the caterpillars doing the damage, are not.

This photo was taken in June not January.

The Winter Moth caterpillar cycle is nearly finished now. They will drop to the ground to pupate. There are foresters very interested to determine exactly how and where they complete this stage, as control may be possible. But, to add insult to injury, Gypsy Moth caterpillars have made a comeback in many areas, as well as Tent Caterpillars, easy to spot with their webby abodes. The poor trees that are trying to re-sprout leaves, are being eaten back yet again. There is only so much a tree can tolerate before it will be damaged beyond recovery. The Gypsy Moth caterpillars and Tent caterpillars are not as enticing to birds; they are too fuzzy to be palatable to most, except Cuckoos. We can wage war on them. Tent structures can be removed and destroyed. Gypsy Moth caterpillars often migrate up and down the tree trunks and can often be found clustering near the base prior to pupating. I have no problem destroying them!

Gypsy Moth caterpillars blend in to the tree bark.

Monarch Butterflies

But then we think of our Monarchs. The beautiful native that has enthralled people of all ages and cultures for centuries is under siege. Their home range for winter migration is threatened with climate change and forest destruction. The Milkweed they depend on here, for their caterpillar food, is being decimated by habitat change and widespread use of herbicides. There is a “lookalike” invasive plant, Swallowwort that attracts the butterfly to lay her eggs, but the caterpillars will not be able to survive.

Monarch butterflies are in serious decline.

Little Monarch caterpillars have big appetites.

So dedicated nature people like me go out to dig, propagate and save milkweed to establish big patches in attractive places for the Monarchs to use. We rejoice to see the chewed up leaves!

We protect the Milkweed plants so Monarch caterpillars can survive. 

Another caterpillar…a different response!

Photographs by Beth Sullivan.