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Photo#339655
Nut weevil - Curculio

Nut weevil - Curculio
Pennypack Restoration Trust, Montgomery County, Pennsylvania, USA
October 2, 2009
Size: 5-6 mm (some smaller)
I picked a dozen nuts from a Chinese chestnut on September 21, the same day in which I found a nut weevil about to start drilling a hole. The weevil didn't survive the chilling for the photo op so it never finished the hole. I still don't know if it is Curculio proboscideus and I don't know if the grubs have anything to do with it.
Update, 12/5/15. This adult was IDed as Curculio sayi

All nuts looked very healthy and without signs of holes that I could see. Anyway, yesterday (October first) these grubs started emerging from three nuts and went on, and on, and on. These morning (October 2) there were 92 grubs (yes, 92!). Eight nuts had several holes and only four seem intact. We'll see; I can almost hear chewing noises. Twenty stragglers emerged today so far.
Most measure between 7 and 9 mm, but there are a few runts, 5 mm or less.
Interesting discussion on acorn and nut weevils and some links.
Update, October 5, three more nuts have weevils, so far only one has none. Total so far: 163 weevil larvae. I will try to raise them in a terrarium.
Compare to the acorn weevils that I found on 10/19/09 and that came from red oak acorns collected on 10/01/09.

Higher res. image

Images of this individual: tag all
Nut weevil - Curculio Nut weevil - Curculio Nut weevil - Curculio Nut weevil - Curculio

Moved
Moved from ID Request.

Chestnut weevils
For what it's worth, I've only come across references to two species of chestnut weevils. Larvae of the larger chestnut weevil (Curculio caryatrypes) exit the nuts in the fall, as is typical of Curculio species in general. The lesser chestnut weevil (C. sayi), however, lays eggs in mature chestnuts and the larvae hibernate within the nuts. So it seems that the former is a likely candidate for these.

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i hope Charlie O'Brien will sort out our Curculio in the foreseeable future and you'll get a name. And these grubs do indeed look like their offspring.

 
Problems with existing keys
The last revision of Curculio was by Lester P. Gibson in 1969. The revision is good but they keys are hard to work through. Don Whitehead (deceased, formerly of SEL-USDA Washington Lab) prepared a key to the eastern species which worked much better but it was never published. I have been in recent discussions with the
SEL lab to see about getting it published.

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