Pemphigus populicaulis, gall on cottonwood - Pemphigus populicaulis

Moved

… MJ Hatfield, 26 October, 2009 - 7:15am

Interesting

As far as I know, that species is only found on cottonwoods, not aspens (although I realize that all are Populus spp.). Sure looks like it, though. Is there a slit to let the inhabitants emerge, as in this one?

I seem to remember coming across a paper in the Canadian Journal of Entomology from the last decade or so that discussed a number of similar aphid galls in poplars, but didn't have time to thoroughly read it at the time. It definitely described some that aren't in Felt (1940) though.
[Edit:] I now see the aphid images you posted separately. I'd suggest moving these to populicaulis for now, and at some point I'll try to find that article again and see if it suggests a different ID. The aphid images should be linked to this one, assuming there was nothing else in the container that they might have come from.

… Charley Eiseman, 25 October, 2009 - 10:06pm

Back side of gall

Charley, I just posted the back side of the same gall. But overall it looks as if I have 2 different Pemphigus galls in the same container, so there is no way to know which gall the aphids that emerged are associated with. Perhaps since the galls are both Pemphigus I can move the insects to family level and leave the galls separate. What say you?

And I should drop the associated galls and insects since I don't know for sure which goes with which. I've been told before not to be so cheap with my plastic bags, put one gall per bag, and this just substantiates that good policy. (Yes, I wash and re-use the bags a dozen times.)

… MJ Hatfield, 26 October, 2009 - 9:55am

Charley, I added two different exit holes (I think?) and cross referenced everything.
Do you know the difference between the slit and the little hole along a line of an unopened slit?

… MJ Hatfield, 26 October, 2009 - 7:40am

The little hole

suggests an emergence hole chewed by chalcid parasitoids--normally the slit parts evenly to allow the aphids (which don't have chewing mouthparts) to emerge. I don't have direct experience or knowledge of chalcids parasitizing aphid galls, but there seems to be a chalcid for just about everything... However, if that's the hole these aphids came from, maybe sometimes the slit doesn't open right and the aphids have to force their way out in the middle or something. I've been noticing lately that all the witch hazel leaf galls I examine have a similar round hole on the underside, even though I'm pretty sure I've seen them with linear slits before.

… Charley Eiseman, 26 October, 2009 - 8:51am

Oops,

You'll see that I changed the host plant (thanks to John), so now it makes more sense.

… MJ Hatfield, 26 October, 2009 - 9:11am

Ah, okay

Can you clarify this one:

Was it from the same tree? I think I've only seen Pemphigus populitransversus galls on aspens, but Felt doesn't specify what kind of poplars they're found on, so cottonwood may be possible too.

… Charley Eiseman, 26 October, 2009 - 9:21am

I don't know

as I picked them up off the ground in a 10-20' area. I'm going to meet with John Pearson next week and have him look very closely at the leaves. I'll let you know.

… MJ Hatfield, 26 October, 2009 - 9:31am