The star of this week’s column is a diminutive wasp in the Gelis genus. Specifically, with thanks to Ross Hill at BugGuide.net, this is Gelis tenellus. These parasitic wasps don’t have a common name, which is a good sign that they’re not very well studied. However, in researching them, I learned enough to know that they’re worthy of more attention.
Many species in the Gelis genus are wasps without wings. Does that sound like an oxymoron? I figure insects are like the English language: There are rules for the families and orders, the grammar, if you will, then there are the many exceptions. The general rule is that bees and wasps have two sets of wings. Gelis wasps are an exception. The females have ovipositors, but the round-ended males look an awful lot like ants. This is by design.
The most studied species of the group, Gelis agilis, has been shown to not only imitate ants in their shape, size, and movement, but it can also fire off a chemical that mimics the spray ants use to defend themselves. Why would a wasp want to disguise itself as an ant? Because ants are notoriously foul tasting. Even though the wasp at Mount Pisgah has wings, I think it probably benefits from the mimicry. As you can see in the photos, at a glance it’s easy to mistake for an ant.
Gelis tenellus is mentioned in many research papers as a hyperparasite, which means that it lays eggs inside other parasites, which are themselves parasitizing a host. Yes, the insect world is a Wild West kind of place. Gelis tenellus is a prevalent parasite of the wasp species Apanteles melanoscelus, and that species was introduced to the U.S. to control the gypsy moth.
Well, gypsy moths are a problem largely in the midwest and northeast, so that’s probably not where this Mount Pisgah female is laying its eggs, but Gelis tenellus also parasitizes other moth parasites as well as moth caterpillars.
My photo is the first on BugGuide for Oregon, but that’s not because I found a super rare species. I think it’s because small creatures that don’t bother humans don’t get much attention.
Research paper on mimicry including two good photos: “Multi-Trait Mimicry of Ants by a Parasitoid Wasp,” Miriama Malcicka et al., Jan. 27, 2015. https://www.nature.com/articles/srep08043. Accessed 11/19/20.
General information: “Wasps Without Wings,” by Valerie (no last name given), May 2012. http://www.austinbug.com/larvalbug/val/archval5-12.html. Accessed 11/19/20.