Life on a maple branch

One of the necessary chores that comes with keeping horses, of course, is having to muck out the stalls. It’s a pleasant sort of physical labour, where you feel you’ve had a good workout and been productive at the same time. If kept on top of every day it’s neither a lot of work nor very time consuming, but can add up quickly if neglected.

It was while I was busy doing this that I noticed today’s subject. I was returning from dumping a wheelbarrow load, my mind on other things (such as wondering how Mom still does this every day, at her age), and so wasn’t paying a lot of attention to bugs or other critters. If this bug had been anywhere else on the maple tree I probably wouldn’t have noticed, but it was at the tip of the very lowest leaf of the branch that hangs over the driveway, pretty much at eye level. And the bug was red and black. Hard to miss.

It was busy laying eggs. Naturally, I didn’t have my camera since I was working in a spot I wasn’t keen on the camera being, so I dashed indoors to grab it and came back to run off a few shots. She was oblivious, focused on the task at hand, I guess, And I was able to manipulate the leaf to pick up the best light (and also to keep it steady and easier to focus on in the light breeze).

When I came back inside and looked it up in my Kaufman guide to insects, it was shown there as a Box Elder Bug, Boisea trivittata. I thought, Elder? What’s it doing on the maple, then? And it wasn’t alone. A few leaves above it was this solitary individual, who seemed to either be lost or looking for a mate as it roamed from leaf to leaf. A few leaves further I noticed a pair copulating (below). I’m not sure if the larger one is the male (as is traditional in many species) or female (since she’s the egg-layer and needs the size to haul them about). They certainly didn’t seem to feel out of place.

Well, it turns out the Box Elder is actually more often called Boxelder, and is not a type of elder at all, but rather a maple, a member of the genus Acer. The Eastern Boxelder Bug, as it’s called on BugGuide.net, is also sometimes known as the Maple Bug, and will lay its eggs on the foliage, seeds or bark of Boxelder and other maple species, and also ashes. So it wasn’t in fact out of place at all. The nymphs, when they hatch, feed on the seeds of the trees, as well as opportunistically on dead insects. The adults primarily feed on the plant’s juices.

Apparently the adults are most often seen in the fall, but are also around in the spring. BugGuide indicates the spring period is primarily May, so what they’re doing out in late June, I don’t know. It could be that the May date applies to a different area than here, since the species is found across most of North America east of the Rockies. Supposedly they can be a house-invader in late fall, as they’re looking for a place to spend the winter, much like ladybugs, but I don’t think I’ve ever noticed them doing that here.

I left the female to it and she finished up laying. When I checked today there were about ten of these small, soft eggs, no bigger than the head of a pin. I don’t really know, but I would guess that the pale crescent you see on one end of the eggs is akin to the yolk of a bird’s egg – the fertilized cells sit on that, and that’s what the developing embryo uses for food.

Edit: Commenter Ted indicates, “The orange crescent you noted on the bug eggs is actually the outline of the operculum, which is the “cap” of the egg – when the nymph hatches, this cap will pop off and out will crawl the nymph. Eggs of most “true” bugs (order Hemiptera) have these opercula, as far as I can tell.” Thanks, Ted!

The branch was surprisingly full of activity for just a little section of tree. While examining the bugs, I happened to notice a light green caterpillar just a few leaves over. I don’t know what species this is, and I couldn’t even tell you if it was a butterfly or a moth, though I’m inclined to think the former. I used to believe that moth caterpillars were hairy and butterfly caterpillars were smooth, but it turns out that either can be either, and so now I know of no reliable way to differentiate the two. The inchworms, though, those little guys with feet at each end, who inch rather than crawl, those guys are moths, as are the really, really fuzzy ones like the Woolly Bears.

I didn’t notice it at the time, but in looking at the photo as I cropped it down, I spotted a white glob at the back of the caterpillar’s head. I’m fairly certain that this is the egg of a parasitic insect, probably a fly. There are a number of species of flies that lay their eggs at the back of the head of caterpillars, where the caterpillar can’t remove it. When the egg hatches, the larva burrows into the caterpillar’s body, and lives there, without killing the host, until it’s ready to emerge (at which point the host usually dies). Some caterpillars, such as tent caterpillars, have evolved a response of rapidly twitching their front end back and forth when they see a fly so that it’s a much harder target to land on.

Also in the area were many of these fuzzy caterpillars. Again, I don’t know what they are, but they were very brightly coloured, and the density and length of the hairs makes me think moths. There were many different instars, or larval stages, of these caterpillars on the branch, from the fairly mature one above, to a middle-aged and even rather young. On a few leaves I spotted the empty, shed skins (below) of caterpillars as they move from one instar to the next.

It’s amazing how much there is to see when you stop to look; if it hadn’t been for that one bug, laying its eggs on the low-hanging leaf, I would have just walked right on by, thinking the branch was empty.