After visiting horsemint, the back and head of the great black wasp are coated with pollen.
Community gardens are fertile hunting grounds for interesting insects. On a recent visit to the West Side Community Garden in Columbia, Maryland, patches of milkweeds, mountain mints, and monardas were humming with pollinators large and small. In addition to the standard bees, butterflies, and flies, a couple of very impressive black wasps were busy in the florets. These were not social wasps like Asian giant hornets, European hornets, bald faced hornets, and yellow jackets, all colonial wasps that live in a nest ruled by a queen. These were solitary wasps, a part of the digger wasp clan. The larger of the two, Sphex pensylvanicus, goes by the name of great black wasp, while its smaller orange-legged cousin, Sphex nudus, is known as the katydid wasp.
As members of the digger clan, female great black wasps and katydid wasps excavate galleries a foot or more deep in the soil. This crypt will serve as the nursery and larder for the developing wasp larvae. Female Sphex wasps search the treetops for those beautiful and melodious nighttime troubadours, the katydids we met last week. Once she locates her prey, she stings and transports her prize back to the subterranean burrow. Inside the burrow she provisions each brood cell with two to six victims and lays an egg on the underside of one katydid. Here is where this macabre tale gives me the willies. The katydids in the crypt are not really dead. They are just mostly dead, like the tortured Dread Pirate Roberts in the movie Princess Bride. Ah, but there will be no Miracle Max to rescue these unfortunate creatures. The venom of the great black wasp does not kill its prey; it merely paralyzes the victim. The moribund katydids are alive but cannot escape the jaws of the wasp larva as it proceeds to consume the hapless prey one by one over the span of about ten days. Whew, makes me glad I am not a katydid. Fully developed larvae spin cocoons in autumn and remain underground through winter, awaiting the return of summer before emerging from the earth to sip nectar and hunt katydids, crickets, and grasshoppers.
Sphex wasps are very fond of mountain mint and spotted horse mint. When the wasp probes the blossom for nectar, anthers dip down and release their pollen on its back.
One of the most curious pollination events takes place as great black wasps nectar at spotted beebalm, a.k.a horsemint (Monarda punctata), one of my favorite flowering plants by virtue of the vast number of insects it attracts. Unlike open-faced flowers such as sun flowers, horsemint provides a curious array of petals, anthers, and stigmas. Nectar fiends like the great black wasp land on petals and, as they probe deeper into the flower, pollen laden anthers dip down and discharge their yellow pollen grains onto the back of the wasp. As the insect moves from floret to floret pollen accumulates, turning the back of the great black wasp yellow. The transformation of the great black wasp to the great yellow-backed wasp never fails to amuse me. Spotted horse mint will always have a place in my garden.
Acknowledgements
The fascinating article, “The life-history and habits of the digger-wasp Ammobia pennsylvanica (Linn.)” by John A. Frisch was used as a reference for this episode. Bug of the Week thanks Dr. Shrewsbury for providing the inspiration and image for this story.