I love a good scavenger hunt. I love the challenge of hunting for something particular, given some guidelines on where to look, and the delight and satisfaction when the target is found. Which is probably why, every winter, I go out one afternoon to see if I can figure out where the tent caterpillars are going to be this year.
It all started when I found a cluster of white eggs on the shiny dark bark of what I think was a young apple tree, in spring of 2008. It had always seemed to me that the white tents of the tent caterpillars appeared as if by magic in the spring. One month there was nothing, the next month there was this large, fist-sized webbing in the fork of a branch. So when I discovered that the moths lay their eggs on the branches – fairly conspicuously, I might add – and that they spend the winter in this state… well. A challenge, if I ever saw one.
That was 2008. Late in the winter of 08/09, I went out and scoured the branches of appropriate trees, deliberately trying to find the egg masses of the tent caterpillars before they hatched out in the spring and started building their webs, and was pleased to actually find some. I did it again last winter, too, though I only mentioned it in passing in another post.
And here’s this year’s cohort. The top photo is of last year’s eggs (laid 2009, hatched 2010). The second photo is of what will become this year’s caterpillars (laid 2010, will hatch 2011). Between laying and hatching, the eggs are covered by a shiny brown, hard shellac-like cover that helps to protect them from the elements and potential predators. When the caterpillars hatch in the spring, they’ll have to chew their way through this cover to get out. The shellacking falls away after this, leaving white eggs with dark holes in the tops – how you can tell the difference between old and new eggs.
After they hatch, the caterpillars move down the branch (toward the trunk) until they reach the first major fork. There, they set up shop and start building their web. This photo is of a clump of new eggs only a handspan above a major fork. I bet you can guess where the nest is going to be, come May.
Tent caterpillars are no more than an aesthetic nuisance – they very rarely cause any lasting damage to the tree – and so I leave them. Out here in our fields, there’s no one to be bothered by a defoliated tree anyway. Once the caterpillars move on to pupate, in late spring/early summer, the tree will have a chance to regroup and fix itself up again before it has to go dormant for winter.
I talked a bit more about tent caterpillar biology in my original post from 2008 (mostly post-hatching info).