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In my last post on nature photography, Ruth commented:

I seldom see unusual animals, insects or birds, but I would like to be able to recognize the signs that they were there, whether by identifying feeding habits, scat, trails, etc. I likely would see more if I knew how to look for the right clues.

I commented that I’d try to write a few posts on finding various creatures, and this is the first.

It’s probably no great surprise to most of you, but I happen to like caterpillars and spend a good deal of time studying and photographing them each summer. If there’s a tree or plant of any kind in sight, then chances are, depending on the time of season, there’s probably a caterpillar somewhere in the vicinity. Keep that in mind at all times — if you look hard enough, you *will* find caterpillars.

Here are a few tips to help you on your way:

First and most important — watch for leaf damage, or branches where leaves have been entirely stripped away. Caterpillars are voracious leaf eaters, so missing or damaged leaves on any plant are almost a dead giveaway that there are caterpillars close by. I’ve sometimes found whole branches on bushes that have been stripped entirely of leaves. That’s pretty much how I noted the Pandora Sphinx (Eumorpha pandorus) in the above photo. Also watch for frass (insect excrement) around damaged leaves. All of that eating results in the creation of a lot of frass.

Now, you may not find caterpillars just sitting out in the open, as in the case of the Pandora Sphinx, but turn a few leaves, or step beneath the branch of a tree, and you may just find what you’re looking for. But, you’ll have to look closely, as most caterpillars are well camouflaged so that they can carry on with the business of eating without much concern for hiding. That was certainly the case with the Schizura in the above photo. If I looked away for even a few seconds, I would have to look very hard to re-find this caterpillar. It’s brown tail-end section resembles the dried curled edges of leaves, making it very difficult to see.

The Red-humped Oakworm Symmerista canicosta in the above photo, was a little more obvious, but it’s surprising how well those lateral yellow lines blended with the veins of the leaves. I don’t think I would have seen it, but Don and I were talking while taking a break at the side of a trail. I first noticed some leaf damage on a nearby tree branch, and after studying it for awhile, I suddenly began to see caterpillars feeding.

Such was also the case with this Hag Moth (Phobetron pithecium) that was prowling over a small Sugar Maple at trailside. Once again, we were just standing around studying the trees and looking for insects when I happened to spy this odd little caterpillar moving over a damaged leaf.

I should probably mention that I regard the finding of caterpillars to be something of a serendipitous thing. I never set out on a walk thinking, “I’m going to find a Cecropia caterpillar today!” because things just don’t happen that way — at least, not most of the time. Instead, the finding of caterpillars is as much luck as anything, especially in the case of final instars as only a very few caterpillars ever make it to that life stage. By far, the majority are eaten by some other insect, or have succumbed to an infestation of some form of parasitoid. If you happen to find a big, healthy Sphinx caterpillar while out for a walk, then consider yourself very lucky.

That said, there are some species of caterpillars that may be found fairly reliably if you know a little about their favourite foodplant. We all know that Monarchs like milkweed, but so do the Milkweed Tussocks (Euchaetias egle). In summer, you will find them, usually in groups, feeding together on Milkweed leaves. The earlier instars are small and more hairless. I think these are probably fourth instars. By the time they are final instars, you likely will not find them in groups like this — just a good-sized solitary caterpillar roaming around over the Milkweed plants. Last summer, I found quite a few while searching for Monarch larvae.

Now, back to serendipity and making it happen. As mentioned above, if you look just about anywhere, you’ll probably find caterpillars of one sort of another. Wherever I happen to be standing, I allow my gaze to rove around through the nearby vegetation, watching for anything that strikes me as even slightly out of place. That’s how I found the Pearly Wood Nymph (Eudryas unio) in the above photo. I was studying a stand of Purple Loosestrife, casually searching for Golden Loosestrife Beetles, when I noticed a bit of brilliance among the leaves. At first, I thought the orange was just the warm brown of a wilted or damaged leaf, but upon closer inspection I found this wonderful little caterpillar.

Sometimes you find caterpillars in places where you least expect them. This is frequently the case with final instar caterpillars that are seeking a safe place to pupate. I believe that’s exactly what was taking place when I found the Four-horned Sphinx (Ceratomia amytor) in the above photo. While walking along a trail at Murphy’s Point Provincial Park in late August, I was scanning the old cedar rail fences as I’ve frequently found Dark Fishing Spiders (Dolomedes tenebrosus) and also Narceus annularis millipedes on the fences at that time of year. At one point, the top rail of the fence is a bit above eye level due to the slope of the trail. I caught a glimpse of the edge of something green sitting atop the rail. I almost walked on, thinking to myself, “Oh, it’s probably just a leaf,” but then something twigged me to step up to the fence and take a closer look. I was both surprised and thrilled to find that the “leaf” was actually this terrific caterpillar.

One final serendipitous way to find caterpillars, especially late in the season, is by checking out tree leaves that are curled to form a tube shape. I frequently find caterpillars inside of curled leaves, within the refuge where they will begin their pupation. That’s how I found the above Tiger Swallowtail (Papilio glaucus) at Mill of Kintail Conservation Area, on Sept. 8, a couple of years ago. There was something just a little magical about this find as the caterpillar seemed hidden away within its own little world.

By the way, as this may well come up in the comments, last summer, I did give “beating around the bushes” with a badminton racket and a collection sheet a brief try, but found that it really didn’t appeal to me. I enjoy photographing caterpillars in situ, so don’t much enjoy displacing them so that they’re writhing around on a white sheet on the ground. I did consider doing a bit of caterpillar rearing to see what some of our caterpillars transformed into (I’ve done this in the past), but got so busy with last summer’s Monarch caterpillar rearing project, that I didn’t bother. Anyhow, for the most part, I’d rather leave the caterpillars happily munching on their foodplants and just enjoy watching them and shooting a few photos.

So, that’s about it for tips. The only other thing I would suggest if you’re seriously interested in caterpillars, is to get yourself a copy of David L. Wagner’s Caterpillars of Eastern North America (assuming you’re in the east, that is). Hands down, I think it’s about the best caterpillar field guide to be found.

Tags: nature photography, caterpillars, Pandora Sphinx, Eumorpha pandorus, Tiger Swallowtail, Papilio glaucus, Pearly Wood Nymph, Eudryas unio, Red-humped Oakworm, Symmerista canicosta, Four-horned Sphinx, Ceratomia amytor, Schizura, Milkweed Tussock caterpillars, Euchaetias egle, David L. Wagner, Caterpillars of Eastern North America