Sawflies

An insect assembled from spare parts.

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Dolerus nitens, the early spring sawfly. Photo by Matt Pelikan

On nearly any decent winter day — sunny, not too cold, not too much snow on the ground — I try to swing through my yard around midday, when the temperature hits its peak. I’m looking, oddly enough, for insects, and while winter isn’t exactly the zenith of insect activity on the Vineyard, a little patience usually produces more than you’d expect.

Often, all I find are the “usual suspects:”  A short roster of insects occurring with some regularity in the winter, species that are either adapted for cold-weather activity or simply common enough and hardy enough so a few examples can be found nearly any day year-round.

But once in awhile something unfamiliar puts in an appearance and I take peculiar pleasure in such a find. It always lifts the spirits to make a new friend under inauspicious conditions.

A week ago, St. Patrick’s Day, was a particularly fine day, and for the season, an especially lively one in the yard. As I ambled across the grass, which was just beginning to show hints of green, a remarkable number of insects took to the air, disturbed by my footsteps. Weak-flying, small, and evidently lacking bright colors, they had me puzzled. But despite their languid flight, they’d land again and disappear before I could pin their location down and get a decent look.

My first thought was that they might be ants, winged males or possibly queens going about the business of starting new colonies. Something about the slow, meandering flight reminded me of such so-called “alate,” or winged, forms of ants I’ve seen in the past. When I finally caught up with one, I realized my first guess was wrong but still suggestive of the right answer.

One individual finally hit and landed on a post of our porch railing, well lit and unobscured, and I was able to sneak in for a close look. My initial reaction was complete confusion: It looked like an insect assembled from spare parts, and each section of the body suggested a different group: wings like a fly, antennae like a wasp, body like a beetle…

But here’s a trick I’ve learned: When you’re totally bewildered by a flying insect, check out the sawflies! Nestled in Hymenoptera, the same order that encompasses bees, wasps, and ants, sawflies are a good-sized group (more than a thousand species in the United States) and show a wide variety of forms. Considered more primitive than the other Hymenotera, sawflies are usually fairly stout insects that lack the thin connection, or “wasp waist,” between thorax and abdomen that wasps and ants show. They’re less hairy than most bees.

If you’re familiar with sawflies at all (most people aren’t), it’s likely with an immature form, rather than adult. Sawfly larvae bear an uncanny resemblance to caterpillars, that is, to the larvae of butterflies and moths. The distinctions are subtle: sawflies have more “prolegs” (fleshy false legs on the underside of the abdomen) than true caterpillars do. And their heads are usually rounder, smoother, and more strongly separated from the rest of the body. Many sawfly larvae are brightly colored, often spotted or striped, and in general they tend to change appearance dramatically as the mature.

Like caterpillars, sawfly larvae eat plants, with each sawfly species usually restricted to one or at most a few related host plants. They sometimes achieve pest status, reaching numbers that can defoliate desirable plants. One sawfly that occurs on the Vineyard is a dogwood specialist, and clusters of its larvae can defoliate one of these ornamental trees in no time flat; other species concentrate on evergreens, likewise sometimes getting locally out of control.

I’ve spent little time working on sawflies, and my sense is that this group is not especially well represented on the Vineyard. They’ve certainly never been carefully studied here. Identification of adults is not easy – species only distantly related to each other often look very similar, and many species look generic, lacking obvious distinguishing traits. But with a little patience I managed a firm ID for the sawflies in my yard: Dolerus nitens, sometimes called the early spring sawfly. Like so many of the insects I find in our heavily settled neighborhood, these are non-native, evidently imported by accident at some point from their home range in Europe.

Moving carefully and now having a sense of what I was looking for, I found scores of adult Dolerus in the grass, most of them basking in the sun as they hugged a green blade. I’ll look for larvae as the season progresses; they feed on grass and likely prefer non-native lawn species sharing the insects’ geographic origin. While I’m surprised that an insect could get this common without my noticing, it’s a good reminder that even in the off-season and even close to home, there are things to find out there.