Galls on henbit in lawn?

This is not exactly a gardening question, but maybe someone here will know: what is capable of causing large galls on henbit (Lamium amplexicaule)? I have a lawn that I keep on the long side and never treat with weed killers, so I get plenty of henbit that flowers this time of year. Only this year many of the henbit plants are bearing a bizarre gall that I've never seen on them before. The galls are greenish, up to 1 cm or more in diameter, and sometimes more than one are fused together, on the stalks under the leaves. When cut open, they have an internal structure something like that of small cucurbits or gourds.
Anyone know what this might be?
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David Sewell, University of Virginia
Charlottesville, VA USA
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I'll bet these people would know: http://www.ext.vt.edu/
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Hmm. A little more digging suggests that gall wasps are associated species in the Lamiaceae family, of which henbit is a member. If that's what it is, the galls would be caused by their larvae.
Either that, or space aliens are taking over my lawn...

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David Sewell, University of Virginia
Charlottesville, VA USA
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Tiny galls I would suspect eriophiad mites, larger ones like you see are likely from very small wasps which come in fruit fly size on up. David Sewell wrote:

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