Overwintering Oak Galls

Last October I spotted a couple of tiny, pearl-like cynipid wasp galls on the underside of a fallen white oak (Quercus alba) leaf.

Gall (2 mm) on a white oak leaf, sporting a tiny springtail (Hypogastruridae).

Gall (2 mm) on a white oak leaf, sporting a tiny springtail (Hypogastruridae).

I stuck the leaf in a plastic bag to see if anything would emerge in the spring.  Meanwhile, I checked Lewis H. Weld’s 1959 Cynipid Galls of the Eastern United States, and the only mention I saw of a gall remotely resembling these had the simple note, “never reared.”

Going through all my bags in April, I discovered that a wasp had emerged from the gall pictured above.

Cynipid wasp from the same gall (0.8 mm).

Cynipid wasp from the same gall (0.8 mm).

Unfortunately, I’m pretty sure this wasp is an inquiline, i.e., not the wasp responsible for the gall, so the identity of the latter remains a mystery.  What I thought was interesting, though, was the appearance of the dry, empty gall on the moldering leaf.  The outer layer had exfoliated to reveal an even tinier cell within, and I don’t think I would have recognized this as the fleshy white gall I had seen in the fall if I hadn’t collected it.


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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6 Responses to Overwintering Oak Galls

  1. Nancy Lowe says:

    Cool Charlie! Why do you think the wasp that emerged is an inquiline? Have you reared it from other galls? Thanks for sharing.

    • Hi Nancy– As with most of my insect ID, I’m going on gestalt, and this looks more or less like other wasps I’ve reared that have been identified by an expert as inquilines (e.g. these). I’ve sent this specimen (along with many others) to a specialist for identification, so I’ll know for sure eventually.

  2. Elisa Campbell says:

    Charley, whatever happened with the galls you collected on Rattlesnake Knob last year? did anything hatch out of those?

    • Hi Elisa — As this post illustrates, I’m just now getting around to sorting photos I took in April. I just checked my specimen spreadsheet, and it looks like I did get at least one wasp from those galls, on April 26. Sorry if I forgot to let you know! I’ll either post or send you a photo when I get there in my sorting. I have a probable ID for the gall too, but I don’t remember the name off the top of my head. I found the same galls last fall on Nantucket, where Quercus prinoides is much more common, and possibly the same ones this spring at the Montague Plains.

  3. willardw@comcast.net says:

    Thank you, Charley. Your reports are exquisite and brilliant.

    Wendy Willard, a fan

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