Gall watchin’ in the barrens

I took my family on a nature walk last weekend in the Scotia Barrens. Usually we go to watch dragonflies skim Ten Acre Pond, but it’s way too early in the season for that. This time we were scouting for cynipid galls on scrub oak (Quercus ilicifolia). They weren’t hard to find, and I counted at least four or five different kinds. I found this one especially interesting:

an open hand holding two spindle-shaped galls; a scrubby tree stands in the background

A pair of galls from the scrub oak in the background. Photo (CC BY 2.0) by Andy Deans. Click for source

Here it is closer up. It’s about 5 cm (2 in.) long, from base to tip:

oak laef attached to a twig. The leaf was converted by a wasp into a spindle-shaped, balloon-like structure (the gall)

Amphibolips quercusilicifoliae (Bassett, 1864) gall on Quercus ilicifolia (bear oak). Photo (CC BY 2.0) by Andy Deans. Click for source

I determined that it was induced by Amphibolips quercusilicifoliae (Bassett, 1864), a gall wasp about which very little is known. The species was originally described by Homer Bassett, a librarian from Connecticut, as Cynips quercus ilicifoliae, and was known back then to occur in Pennsylvania and Connecticut. The phenotype of these galls seems quite similar to other species of Amphibolips, like A. acuminata. There’s probably a cool project here. Maybe when it warms up we’ll head to the barrens for some fresh galls.

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