Small Wasps Can Warn of Big Issues

Columns - IPM Insights

While servicing an account, a PMP might encounter small, parasitic wasps. An occasional one of these wasps indoors could simply be an accidental invader from outside (and a nuisance to the customer), but multiple wasps may represent a more complex issue. Similar to a physician diagnosing a disease from its symptoms, an astute PMP may diagnose and ID a hidden pest infestation by being able to accurately identify these wasps.

Parasitoid wasps lay their eggs in/on other insects. As these eggs develop inside the host, they consume it from within and kill it as they emerge. The concept of wasps indoors can potentially be upsetting to customers, however, these parasitoid wasps are actually on our side. Not only do they reduce some of the pest population, but they can also alert a sharp-eyed technician of a pest infestation they may not know exists. Gardeners should be especially appreciative of these wasps, as they are often parasitoids of plant-feeding insects such as caterpillars and aphids. Additionally, some parasitoid wasps are sold as a biological control method for pests such as house flies — a very underutilized step in the IPM process!

Here are three different parasitoid wasps that may help a PMP hone in on a hidden pest infestation.

ENSIGN WASPS. Ensign wasps (Figure A) are a family (Evaniidae) of slender black wasps about one-quarter of an inch long, possessing a thin waist (petiole) and a small, triangular abdomen (gaster) that is held above their body, giving the appearance of a waving flag (or ensign). They are parasitoids of cockroach egg cases (ootheca) and target larger roaches such as American and smokybrown cockroaches.

CHALCID WASPS. A family (Chalcididae) of small, stout-bodied wasps with short antennae, chalcid wasps are easily identified by their enlarged hind femurs (rear upper legs). One species in particular, Brachymeria podagrica (Figure B), about three-sixteenths of an inch long, frequently parasitizes filth fly larvae and can be indicative of a dead animal in a structure.

BRACONID WASPS. One of the largest families (Braconidae) of wasps in the world, braconid wasps are typically small and slender with long antennae. They parasitize many different soft-bodied insects, as well as plants (as gall-formers). They are known to parasitize filth fly and Indian meal moth larvae, and, in the case of Apanteles carpatus (Figure C), which are about one-eighth of an inch long, both casemaking and webbing clothes moth larvae.

FINAL THOUGHTS. Next time you are servicing an account and see a small wasp, take a closer look. It might just point you to a hidden pest problem!

The author is a Board Certified Entomologist and PHE certificate holder. He is the director of quality and technical training at ABC Home & Commercial Services in Austin, Texas.