Subject: Gall Insect
Location: Fairfield, California
March 28, 2016 1:40 pm
I have a couple oak galls in a sealed bag and this morning, I found this brilliant green insect walking around on the exterior of one of the galls. I was not expecting to see such a beautiful insect since the gall wasps with which I am familiar are usually black! The galls were collected from the ground under an unidentified species of oak on March 23, 2016, in Fairfield, California. The insect is approximately 3/8 inch in length. Thanks for your help!
We are going to go way out on a limb in our response because of the interesting information we have learned while researching your request, and then we will consult Eric Eaton to see how far afield we have gone. We tried researching green gall wasps and we stumbled upon an image that led us to a Nature Conservation Imaging where we learned the wasp in the image is a Pteromalid in the family Pteromalidae and that “The thousands of other parasitic wasps include the Chalcidoidea, which tend to be tiny and are often known as chalcids. There are more than 1,000 species in Europe including a good number of Pteromalid wasps (3mm). They are predominantly parasitoids, affecting a wide range of insect groups. A few are parasitoids of the larvae of gall wasps, so can emerge from galls, but they are not the causers.” We then turned to BugGuide to see if we could find any visual matches, and we cannot say for certain that your Wasp resembles any definitively. The antennae on your wasp are quite distinctive, and we will get back to you once we hear from Eric Eaton.
Eric Eaton sets us straight
Neither. This is a cuckoo wasp, family Chrysididae. They are parasites of other solitary wasps, and solitary bees, and perhaps one of the host insects nested inside an abandoned gall and the cuckoo wasp followed it inside.
Thank you so much for your fast response! I think you are right on track! Through the awesome power of the Internet, my pictures found their way to UC Davis Professor of Entomology Robbin Thorpe and this was his response:
“The beautiful bright metallic green critter in the photos Sharon Leos submitted is a cuckoo wasp, family Chrysididae. Most are parasitic on aculeate wasps and bees. Some of which will nest in cavities like the emergence holes in oak galls. Check out the family Chrysididae on Bug Guide for more illustrations. For more information on the group, contact Dr. Lynn Kimsey, the Director of our Bohart Museum of Entomology. Lynn is an expert on the group. She should be able to identify the critter in more detail. Lynn can be reached at: firstname.lastname@example.org. Regards, Robbin”
I look forward to hearing what you learn from Eric Eaton, as well. Thank you so much! Have a great day!