Currently viewing the category: "Parasitic Hymenopterans"

Dear Bugman:
I live in the San Francisco Bay area of Northern California, and for the last week or two we have had a new kind of bug flying in large numbers around our house. I’ve included some pictures of them so that you know what they look like (I apologize if the size of the e-mail causes any problems for you.) At first we thought they were just mosquito hawks, but on further examination they are much uglier. They are nocturnal and attracted to light, and we have perhaps a dozen a night or more swarming around our outside lights, and usually a few that get inside the house. They are about an inch to an inch and a half in length, and are one of the more disturbing bugs I’ve seen. They don’t seem to match up with any of the pictures I found of termites or flying ants, but I really want to know if they are since that would be a big problem for the house! At about the same time these bugs appeared, there also have cropped up a couple of spots on the lawn where the dirt looks almost bubbly – I have no idea if that’s related, but I thought it may be some kind of nest. Please let me know what kind of bug this is so I can stop worrying or get rid of them, whichever is appropriate.
Thank you very much.

Dear Helga,
Seldom do we get such a concise description accompanied by such wonderful documentation. There is no speculation regarding my identification. You have a species of Ichneumon wasp, Family Ichneumonidae. These are small solitary wasps which have smaller and slenderer bodies and legs than social and semi-social types. The abdomen is compressed from side to side. Some species are as small as gnats, and the larger ones are up to an inch in length. The specimen you photographed belongs to the genus Ophion. All Ichneumons are parasitic on other insects, and many feed on caterpillars. According to Hogue, "The eggs are inserted into the body of the host by means of the females short sharp ovipositor (which incidentally can penetrate human skin). The larvae feed on the internal tissues and, when mature, pupate within the host." They are important biological controls for many agricultural pests. Your possible nest is obviously something else. The adults are often attracted to lights at night.

Thank you very much. Now I can stop worrying. 🙂