Relative to other caterpillars, slug caterpillars seem more fantasy than reality.
~David Wagner
It is getting to be that time of year – caterpillar time! As summer draws to a creeping close, one of the things that lifts my spirits above the stifling heat waves is the increasing abundance of larval Lepidoptera. And one of our favorite groups, the slug caterpillars, is starting to show up in greater numbers in our woods and yard. Earlier this week, Melissa was out in the garden and harvested some of our collards, since it was obvious they were becoming riddled by insect chewing. When she pulled one leaf she saw two tiny Saddleback caterpillars, Acharia stimulea. The female moth tends to lay clusters of eggs and the young feed gregariously at first. They are extremely variable in their choice of host plants. We have found them on tomatoes, various tree leaves, iris leaves, and now, collards. This may be why so may people recognize this as one of our most common so-called, stinging caterpillars as you can find them almost anywhere. You may accidentally brush up against one while weeding your garden and you won’t soon forget that encounter as they pack a powerful punch resembling the pain associated with a wasp sting. You can read more about them in an earlier blog post here.
Two tiny Saddleback Caterpillars feeding on a collard leaf (click photos to enlarge)
They are already sporting the pattern that gives them their name – the distinctive brown saddle outlined in white in the middle of their back
Ballpoint pen tip for scale
Though these guys are extremely small (the tiniest Saddlebacks either of us has ever seen), I think they have probably molted at least once already. Online descriptions say that the earliest instars lack the prominent tubercles on either end.
After one day, the caterpillars’ colors had already darkened and taken on more of the pattern of later instars
One scientific study I found said it was extremely difficult to accurately determine how many times this species molts during its larval development since the head capsule is hidden beneath the body and they almost always eat their shed skin. It is certainly more than the usual five molts of many butterfly and moth species, and may be as many as eleven or more and may require several months before pupation. Once again, I’m afraid we have taken on more than we bargained for in raising some caterpillars (we still have a few Cecropia larvae that hatched on June 10!). But, Saddlebacks will eat a variety of leaves are are not nearly as voracious in their feeding habits as most other species. I’ll try to keep you posted as they mature.
What they will look like in a month or two
