Crabronid wasp
It may be quieter around here in summer, but new opportunities for natural history study buzz by more often too. I was lucky enough to block the particular location where this wasp wanted to bury a paralyzed fly at the bus stop near the UW Medicinal Herb Garden last week, so I got to take a few good pictures of her and talk about the amazing world of parasitoids with members of the university public. (I caught the next bus.)
Although she looks rather like a standard Polistes paper wasp, paper wasps make relatively large paper nests hanging in sheltered locations like your eaves or utility shed and bring caterpillars to their young there. Dragging a fly into this crack didn’t fit that scenario very well.
So I turned to the amazing community at Bugguide.net — I gave them the pictures to post as part of their guide, and they figured out where they should go. Experts there have identified the wasp to subtribe Crabronina so far.
Crabronids are called “digger wasps” and are not dangerous to people, contrary to the concerns of my bus-stop compatriots. Flies are another story. The wasps stock their underground nests with paralyzed prey and lay eggs on each. As they grow, the larvae consume the prey, often creepily referred to as “provisions” in the literature. Then, on becoming adults, they switch to eating high-energy nectar to fuel their own mating and hunting.
| I’d never seen a wasp carrying paralyzed prey before and felt very lucky to get such an extended look. It’s fascinating to me that she investigated the horizontal cracks between the railroad ties in such detail, right in the exact area where the vertical crack she wanted was. A few huge mammals in brightly colored clothing weren’t going to confuse her tiny pattern-matching brain! Eventually the bus stop emptied out and I moved — she zipped directly to her nest, went in, and came out a few minutes later, lighter by a fly and, I assume, an egg. — KMP |
