One of my favorite late summer and early autumn bloomers is spotted horse mint, Monarda punctate. During this season, horsemint attracts an amazing variety of pollinators including Great Black Wasps, Mason Wasps, and Potter Wasps we met in previous episodes. Among the most interesting and beautiful of these visitors are thread-waisted wasps in the family Sphecidae. One of the most common members of the sphecid clan visiting horsemint is Eremnophila, hunters of caterpillars, grasshoppers, and crickets. These morsels are not food for the adult wasp. No, these six-legged delicacies serve as food for their larvae. To find and subdue prey requires loads of energy and frequent trips to flowers for carbohydrate-rich nectar are regular daily activities. When not feeding on flowers Eremnophila seek food for their young. Upon encountering a potential victim such as a prominent caterpillar, the female wasp wrestles with the larva and delivers a paralyzing sting. The immobilized victim is then transported to a subterranean nursery and deposited within. An egg deposited on the hapless victim hatches into a legless larva that consumes the living but powerless prey. Before leaving her young, the mother carefully arranges pebbles and dirt to disguise the entry to her nest. This probably keeps other insects from robbing her larder or making a meal of her young.
Capturing caterpillars requires a lot of energy. While ignoring her piggy-backing mate this thread-waisted wasp fuels up on nectar before the hunt for caterpillars.
Mating behaviors of Eremnophila include prolonged coupling of the blissful pair with the male grasping his mate by the neck as she saunters from blossom to blossom. In addition to spotted horsemint, thread-wasted wasps frequent goldenrods and other summer blooming members of the aster family. When your late summer rambles take you to the meadow, try to catch a glimpse of these clever hunters as they fly in tandem amongst the blossoms.
Interesting and entertaining accounts of thread-wasted wasps including “The habits of aculeate Hymenoptera” by William Ashmead, “Sleep in insects: An ecological study” by Phil and Nellie Ray, “Insects: Their natural history and diversity” by Stephen Marshall, and “Predatory Wasps (Hymenoptera) of the Yucatan Peninsula” by Maximiliano Vanoye-Eligio, Virginia Meléndez Ramírez, Ricardo Ayala, Jorge Navarro and Hugo Delfin-González, were used as references for this episode.