It’s been very rainy here the last couple of days – since I finished and mailed off the moth guide, basically. As if the weather knew that I’d suddenly have lots of time for hiking about and enjoying the last of autumn. Since I haven’t been out (I’m very much a fair-weather hiker, or at least not a poor-weather hiker), here’s another photo I’ve had collecting dust on my hard drive for the last week or so.
I noticed this wasp on a short stalk of goldenrod as I was walking back from checking out the earth tongues. A wasp on a goldenrod is not in itself all that unusual. Wasps seem plentiful at this time of year, but they’re nearly all Polistes paper wasps. This wasp looked strange, and when I peered closer its pinched abdomen, with swollen, bulbous tip, was pretty obvious. I couldn’t recall having seen a wasp of this shape before (mud daubers also have very thin abdomens, but theirs are thinner for longer, and very distinct), so I took a photo and looked it up in my trusty Kaufman Guide to Insects when I came home.
As it nearly always does, the KGI had the answer. This was a potter wasp, most likely Eumenes fraternus, a widespread wasp of eastern North America. According to BugGuide.net, this species favours scrubby fields and forest edges, which is appropriate to the habitat I found it in, and can be found from mid-summer through fall at more northern latitudes like here. Adults feed on nectar, and are often found on flowers.
The name of the group, potter wasps, comes from their habit of sculpting their nests from mud. The cells of the nest are adorable little spherical creations with a flared opening that look like tiny clay jugs. These are provisioned with caterpillars or small sawflies, an egg is laid on the prey item, and then the chamber is sealed off until the new adult wasp is ready to emerge. Larval wasps will spend the winter in their pots.
Raven was a bundle of energy today, so I ended up breaking from work a bit earlier than usual to take her out for a walk and hopefully tire her out enough that she’d sleep through the afternoon and let me get a few hours of solid worktime in. I took her out to the woods so she could run around off-leash for a bit, which burns more energy than simply walking on a leash along the road. Upon reaching the woods I sat her down to unclip the leash (an exercise in patience and discipline more than a requirement for getting the leash off), and noticed, on the ground between her front paws, this wasp. I steered her around it to prevent her from accidentally crushing it, and then while she scamped off to roll in the leaves a short distance away, I squatted down and ran off a few shots.
It’s a parasitic wasp of the family Ichneumonidae (drop the “ae” from the end to give the common name, ichneumonid wasps), subfamily Ichneumoninae. This subfamily is the second-largest of the ichneumonids, and among the most diverse. These wasps are parasites of caterpillars, laying their egg inside the host’s body, where the wasp larva develops and then emerges as an adult (inevitably killing the caterpillar, of course). Females are identifiable from males by the pale bands on their antennae (males lack these, or have indistinct bands), and are often found crawling on foliage or among the leaf litter looking for caterpillars, which may explain the situation with this individual, although it seems late in the season for her to be searching out a host. In fact, the 6 C (43 F) temperatures are not really favourable to most insects, so it was a little surprising to encounter her at all. Kaufman’s Guide to Insects notes that the females of some species hibernate as adults in protected spots such as under loose bark on logs or stumps. I don’t know what species she is (ichneumonids are difficult to identify to species simply from photos), and Kaufman doesn’t specify anyway, but perhaps she was searching out a hibernation spot.