Tay Meadows Tidbit – Great Black Wasp

Great Black Wasp

Apparently Nature felt that I hadn’t been out to visit enough recently, and decided to come to me. I’d just gone into the washroom to return the tea I’d rented (as my dad likes to say) and was startled to discover a GIANT BLACK INSECT squirming at the water’s surface. It was big, at least an inch and a half (35mm) long. And, it turned out, it was a wasp. Big + wasp don’t usually go hand-in-hand as a favourable combination to me (although, I did profile some gentle giants last year; this one was close to the size of those, though not so robust), so I was a little intimidated. I scooped it up in a container and took it outside where I took some photos while it dried out, then let it fly away.

Appropriately, the insect is called a Great Black Wasp (Sphex pensylvanicus). BugGuide lists their average size as 25mm (1″), but this individual was definitely larger than that. BugGuide also remarks that males are smaller than females, so given the size I would suspect this to be a female.

Another clue might be the large mandibles you can see below her face. Great Black Wasps also go by the name “Katydid Hunter” or “Steel-blue Cricket Hunter”. The females capture katydids and crickets – sometimes as large or larger than they are – paralyze them with a sting, and carry them off to their burrow nests. There they lay an egg on the still-living katydid. When the larva hatches, it feeds on the katydid. Paralyzing the prey, rather than killing it outright, prevents the prey item from becoming dessicated or decomposing before the egg hatches. The young overwinter in the burrow; adults emerge and are present in July through September. Interestingly, while the adult catches katydids to feed the young, it itself actually feeds on nectar from flowers. I don’t know what this one was doing inside – there are neither katydids nor flowers in the house, not even dirt that it could burrow in.

Some interesting studies have been done with digger wasps of the genus Sphex. When females return to their burrow with their prey item, they drop the katydid at the nest entrance and go inside just to make sure the coast is clear before they drag the cumbersome object in. If they went in with their mouth full they could be caught in a compromising position that might make it difficult to defend themselves. If a researcher moves the katydid a few inches from where the female dropped it, when she returns outside she has to search for it again. She can find it, but then upon returning to the nest must drop it and inspect the burrow again – her genetic programming forces her to go through this behavioural sequence each and every time, no matter how many times the researcher moves the katydid. Some have cited this as an example arguing against the idea of free will, but I suspect the genetic programming in most insects is probably much simpler than it is in vertebrates.

Great Black Wasp