Blue Oak Gall - Feron crystallinum

Moved

Moved from Cynipini.

… Joyce Gross, 26 September, 2013 - 10:12pm

Andricus crystallinus

This is Andricus crystallinus. I'm not sure why some of them are missing all the pink fuzz. Possibly they are parasitized but that's only a theory at this point. Also, some of them have no hairs, some have a little, some have more, and some have lots. I haven't done enough rearing of these to know if the parasitoid theory is correct or not. Perhaps it's just normal variation within the species.

… Joyce Gross, 24 September, 2013 - 9:49pm

Thanks for the ID, Joyce

The lack of pinkish-red, glistening fuzz...and the shorter-than-wide "onion-dome" shapes...made me think these were something else.

The leaf had already been detached for some time before I took the photo. It was quite dried-out and crispy-yellow. Perhaps the connection to the host's nutrient and moisture supply were cut-off before the galls were able to complete development? But then again, the galls look so nice and vibrantly red...not faded and shriveled.

… Aaron Schusteff, 5 October, 2013 - 5:08pm

development

Andricus crystallinus galls do tend to be less hairy when younger (I think), and the galls in your photo don't seem fully developed (yes, they're short). So it's possible the nutrient situation effected them. On the other hand, there were lots of similar-looking galls on green leaves the same day -- mostly taller galls, but a few shorter ones as well, without hairs. I put some of my photos here.

On a related topic, at Mt Diablo I found singed oaks (after the fire) with dead-looking (but not black) leaves that still had bright-red/pink A. crystallinus galls on them. And more of the bright-red/pink galls lying on the blackened ground. One of the galls even had a live pupa in it!

… Joyce Gross, 6 October, 2013 - 4:00pm