What kind of beetle grub could this be?

[MadMilli]

Any ideas? It was found in Massachusetts and is the biggest I’ve found in the state.

 

[chanda]

From that picture? Impossible to say. But even with a better picture, most of the Scarabaeoidea look pretty similar to one another. Often, the only way to tell them apart is to examine their raster pattern (the pattern of hairs, spines, and bald patches on their "butts") under a magnifying glass and compare it to a key for scarab larva identification (if you have one) - or to wait for it to pupate and emerge as an adult, which may take a few years. (I raise Dynastes grantii, and they typically take almost three years from egg to adult.)

If it is a large larva, you can assume that it will also be a large beetle - but keep in mind that the larva is frequently larger than the adult beetle by the time it is ready to pupate. If it is a small larva, you really can't tell - it could just as easily be the larva of a small beetle that is nearing pupation - or the larva of a much larger beetle that has only recently hatched from its egg and still has a lot of growing to do.

 

[mantisfan101]

Yellow head capsule could mean either a lucanid or a jewel scarab. Look at its anus; is it a vertical or horizontal slit? If it’s vertical, similar to a human butt, them it’s most likely a lucanid, either Lucanus capreolus or Dorcus parallelus. It could also be a goldsmith beetle or pelidnota punctata if the slit it horizontal. What type of environment did you find it in? Rotten log, in your lawn, etc.

 

[Elytra and Antenna]

You probably found it in or under a rotten log (root, stump) and it is likely P. punctata. If that black mark near the end is damage it may not reach adulthood.

 

[MadMilli]

You probably found it in or under a rotten log (root, stump) and it is likely P. punctata. If that black mark near the end is damage it may not reach adulthood.

Yes I found it in a rotting log. There were other medium sized grubs that looked different in there but were significantly smaller than the ones I collected. These are very large for my area, probably larger than the tip of my thumb to a little past the first bend at the first knuckle. I thought the black Mark was damage as well but it appears to be a leaf from the dirt pressed up against the glass, I have 9 other grubs of that size anyway.

 

[MadMilli]

Yellow head capsule could mean either a lucanid or a jewel scarab. Look at its anus; is it a vertical or horizontal slit? If it’s vertical, similar to a human butt, them it’s most likely a lucanid, either Lucanus capreolus or Dorcus parallelus. It could also be a goldsmith beetle or pelidnota punctata if the slit it horizontal. What type of environment did you find it in? Rotten log, in your lawn, etc.

I found it in a rotting tree limb that was laying against the ground. There were 9 of this size imbedded in the bark. Largest grubs I’ve ever found in New England, I’m hoping it’s one of the first two you mentioned. I’ll check the slit and let you know.

 

[MadMilli]

Looks to be horizontal in the back but it has pinchers so not sure.

 

[mantisfan101]

Probably pelidonta punctata like E&A said before.