These wasps were BIG, and they seemed agitated, circling and circling the drain and chasing off other insects that occasionally approached. But once I glimpsed the shiny blue wings atop their jet-black bodies, I knew I could draw near to observe them without any fear. For these were the solitary digger wasps called the Great Black Wasp (Sphex pensylvanicum), a remarkably non-aggressive wasp that has no interest in stinging humans, saving its stinger only for its prey.
We saw some actually carrying their prey! And lucky for us, one wasp dropped its burden where we could get a good look at it. A bright-green Katydid! Doubtless, it had been paralyzed and was still alive, and in fact it was still twitching its antennae when I bent to take this photo.
While we watched, enthralled, the wasp returned to snatch up the Katydid and promptly carried it off to an opening in the storm-drain's grid.
And there it goes, down into the drain! You can see the Katydid's green leg protruding from below the wasp's abdomen.
Wow! How excited we felt, so lucky to be able to witness this amazing insect activity!
When I poked my camera through the grate, this is what my zoom lens captured: a veritable Katydid graveyard, with numbers of bright-green bodies strewn across the damp gravel at the bottom of the drain. What's happening here, I wondered. Don't digger wasps stuff their living insect prey into the tunnels they've dug and then lay their eggs on them? I know that's what Grasshopper Hunter Wasps do, and so do Cicada Killers. Were these wasps going to return at a later time and bury their prey?
When I got home I did some research and discovered that Great Black Wasps do bury their eggs in tunnels they've dug in the earth, but then they lay their insect prey on top of the ground, near to where the eggs are buried. When the eggs hatch and the larvae come up from under the ground, a Katydid feast will be waiting for them, right next to where they emerge. Well, I learn something new every day!
Another thing I learned while researching the Great Black Wasp is that they have another common name. I bet you can guess it, can't you? They're also called Katydid Hunter Wasps.