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what ARE they? - Andricus gigas

what ARE they? - Andricus gigas
Wolf Creek, Josephine County, Oregon, USA
September 9, 2009
Size: 1/16 inch
eggs? fungus? not galls cause they pop off like an egg.
on an oak leaf.

Images of this individual: tag all
what ARE they? - Andricus gigas what ARE they? - Andricus gigas

Moved from Gall Wasps.

gigas vs parmula
The oak must be Quercus garryana, which goes by the common names Garry Oak or Oregon White Oak or Oregon Oak. It's a white oak.

I lean towards Andricus gigas for the gall wasp species, but I'm not able to see all the details in this photo that would make me 100% certain that it isn't A. parmula. It has to be one or the other.

A. parmula is glossy (no hairs). The "bump" in the middle is more of a (very slightly) detached structure in A. gigas than in A. parmula. The middle bump is really just a bump in A. parmula. A. gigas often has toothed edges, but sometimes the edges can be smooth like in parmula. Both species occur on Garry Oak.

I have these photos in CalPhotos you can compare your galls with:
Andricus parmula
Andricus gigas

If you can have a really good look at the details of your galls, it should be clear which galls they are based on the above info. Look especially for hairiness versus glossiness.

yep thats the right oak. its oregon white oak and i also have california black oak.

that's right
... you have black oak up there too, and black oak wouldn't have these galls. The wasps are very fussy. :)

i allways have to study on it awhile..which is from oregon and which from california? now i am from oregon and 6 generations of my family before..unusual these days.

Common names can be misleading:

Quercus kelloggii -- California black oak -- is native to both California and Oregon.

Quercus garryana -- Garry Oak or Oregon White Oak or Oregon Oak -- is native to California, Oregon, and Washington.

Andricus gigas doesn't occur on black oak.

Just saw your second photo and I'm quite sure they are gigas now.

Moved from ID Request.

Cynipid galls
There are, in fact, wasp galls that pop off the leaf easily, and that's what you've got here. Do you know what species of oak this is?

ha! its white oak , but i can
ha! its white oak , but i cant remember right offhand, which white oak
but they sure are cute..what sort of predators are these wasps?

Not predators
I'm not sure if adult gall wasps do anything besides mate and lay eggs... at most they might visit flowers. It will probably be possible to determine what species these are, but it will be a little while before I get to it, and Joyce Gross may beat me to it.

shall i keep them then? i ben wondering if picking a leaf makes a difference to them? i mean the leaf drys out then..

Picking a leaf could cause wasp larvae to dry out and die if the galls aren't fully developed, but if these galls are popping off easily, I'd say they're probably "ripe." Could be a while before the wasps emerge though... I know some of these dehiscent (popping off) galls overwinter in leaf litter before the adults emerge.

i think i found it..
i think i found does this sound??Gall Wasps (Cynipidae) » Andricus » Saucer Gall Wasp (Andricus gigas)but then it said that can be mixed with disc gall wasp..and i cant find that.

Probably close...
but note the statement under that image, "may be confused with those of Disc Gall Wasp (Andricus parmula) if not carefully examined." Doesn't say what the difference is, but if you can find a copy of Ron Russo's book, that will say... I'll check my (older) gall book when I'm home next.
Here's the correct thumbnail (you had a 4 instead of a 1):

I flipped through a gall book...
Key to American Insect Galls (EP Felt, 1917) and while I didn't actually go through the key, I found a few illustrated galls that look similar to this one. In particular, the galls of the cynipid wasp Dryophanta discus and the gall midge Cecidomyia poculum seem to match. Interestingly, the galls of C. poculum were shown to resemble the one in the thumbnail when occurring on Q. muhlenbergiae and to resemble the one in the posted photo when occurring on Q. alba.

Of course, the probabilities are pretty good that these species' names may have changed since 1917.

Dryophanta discus is a synonym of Andricus parmula, which Felt (1940) (1) calls the "oak saucer gall." He lists valley oak as the host--I guess that only occurs in California, but maybe this wasp also uses a related species in Oregon? Gagne (1989) (2) makes no mention of any midge with the species name poculum. I'm not sure what species that would be, but according to Gagne there are no complex (e.g., detachable) midge galls on oaks. Perhaps Cecidomyia poculum was an inquiline of a cynipid. Also note that both Quercus alba and Q. muehlenbergii are eastern species. I hope someone with Ron Russo's book will comment.

[edit]Oh, I guess we have some images of A. parmula. The guide page says it is found on "most white oaks."

Doesn't seem like necessarily a perfect match to me...

stand by for a new picture
i been keeping them in i recognise them as something i saw before..

You're much more thorough than I am.
I didn't even consider the range (duh) and I am fearfully ignorant about oak species.

I am looking again at my 1918 Felt book and there appear to be many descriptions of additional button galls that might be the right one, but I was lazy and just skimmed the drawings. The entry for C. poculum Osten Sacken reads:
"Oak spangles. Saucerlike, small galls frequently on the underside of the leaves, usually clustered and varicolored, diameter 3-5 mm, on Q. alba, Q. macrocarpa, Q. obtusiloba." There is also an image of this species on Q. muhlenbergiae.

You may be right about the midge being an inquiline, but I did find some modern references indicating that this species forms oak spangle galls.

So in summary, I have no practical or helpful suggestions, just some wild stabs based on a haphazard glance at a 91-year-old book. Glad I could help! ;)

I second what Charley says about Felt's book. It has lots of good info in there that is nowhere else. I have a copy of the book for that reason. But for west coast oak galls, it's better if you can get a copy of Russo's book. Even that doesn't have all the western oak gall species -- there are quite a few undescribed ones (some in Russo's book, many not).

Nothing wrong with old sources...
Sometimes with galls, leaf mines, etc., the answers are either in old sources or nowhere at all. I'm reasonably certain that all of the online sources that mention C. poculum are either using Felt (1940) as a reference, or some other source that in turn used that as a reference. Or maybe even your 1918 version. Despite many out-of-date names and a fair number of errors, Felt (1940) is still the best gall reference for non-midges... but Gagne trumps Felt for anything having to do with midges. The privately published cynipid guides by Weld (e.g. (1)) are presumably better to use than Felt, but I have yet to see them. And in western states, Russo's book is more current than all of these, if it happens to have the galls you're after.

yes i saw that
and i couldnt seem to find a way to remove it.
yes what you said.
still i enjoyed disc-overing something new tee hee.

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