Gall Wasp Parasitoid

Greetings from sunny Davis, California!  Although I’m on a quest for leaf-mining insects, it’s hard not to get distracted by the diversity of bizarre cynipid wasp galls on the various oaks around here.  Today I got to see a torymid wasp ovipositing in one of the spiky pink galls on Valley Oak (Quercus lobata).  (See this post for an explanation of what’s going on here.)  Every day on this trip I’m finding many things worth writing about, but since I have no time for that at the moment, I figured a few photos are better than nothing.

Added 9/19/2013: This is a “spined turban gall,” caused by Cynips douglasii.

About Charley Eiseman

I am a freelance naturalist, endlessly fascinated by the interconnections of all the living and nonliving things around me. I am the lead author of Tracks & Sign of Insects and Other Invertebrates (Stackpole Books, 2010), and continue to collect photographs and information on this subject. These days I am especially drawn to galls, leaf mines, and other plant-insect interactions.
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2 Responses to Gall Wasp Parasitoid

  1. charles e guevara says:

    Thanks Charley for the images and your experiences. Here in central NY spittle bugs have a lifecycle with spring egg hatch to 5 instar stages of ‘foam enclosed spittle bug’..eventually the adult ‘froghopper’ leaves the foam nest. Only one complete sequence a year, with the laid eggs overwintering to hatch in next spring season.

    My curiosity: do the torymid wasps have several lifecycles a year? Do the mature oak leaves of one growth season ‘host/tollerate’ various generations of wasp-induced galls? Can various stages of gall formation be observed to occur on oak leaves? thanks for your shared nature studies. charlie guevara, fingerlakes/NY

    • Hi Charlie — My understanding is that most gall wasps have alternating generations, making one type of gall in the spring and another in the fall. Some wasps will lie dormant in their galls for years before emerging, though, so it’s not quite that simple. I don’t know very much about the parasitoid life cycles, but I think that pretty much anything you can imagine is done by one species or another. In my own experience, parasitoids of gallmakers and leafminers tend to emerge well before their hosts would have, so they may have more generations than their hosts; also some may have multiple hosts. For torymids, which can drill into fully developed galls with their long ovipositors, I would think timing is less important (whereas a wasp with a short ovipositor would probably have to get to the gall when it is first developing). Hope that answers some of your questions.

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