What do these turn into?

[Exoskelos]

I'm not a beetle guy, so I don't know what these grubs turn into, but they are MASSIVE. Found two while gathering millipede substrate from the rotten heartwood of a tree. Location SE Ohio.
Anyone know what kind of beetle they become? They baffled me cause I've never seen grubs this big. Pics for reference, compared to a small KK lid and a normal soda can, they're larger than a half dollar when in their "C" shape. I'm guessing I should give them the same type of really soft wood dirt they were eating as a substrate. I would mix up some flake soil, but I'm out of sawdust.

 

[Psydeus565]

I'm guessing some member of the genus Continis.

 

[Exoskelos]

I'm guessing some member of the genus Continis.

I think they might be Dynastes tityus, but honestly I have no idea. Found a bunch of cast off elytra but I'll have to go back and get some to photograph. I think it might be impossible to tell by looking at the larvae.

 

[Exoskelos]

I went back to look for more grubs and the old beetle shells but apparently I buried the elytra inadvertently while digging. They were an olive/OD green color with dark spots on them. If these grubs turn into the beetles I think they do, how to care for them?

 

[lostbrane]

I’m going to agree with D. tityus. Appears to be an L3. Based on size, their appearance, and them feeding on hardwood I’d be surprised if it wasn’t. Adult care is pretty simple. Keep them in a substrate of rotting hardwood (larva eat the sub) that is kept moist, anywhere from four to six inches worth (although I have seen people keep adults on shallower sub/larva in deeper). Might even want to put some plastic wrap over whatever you are using as an enclosure to keep the moisture levels a bit more constant. The adults feed on fruits (without the skin since their jaws can’t break through it), a mix of real maple syrup and water, or beetle jellies.
As to the enclosure, you’ll want a decent lid for the adults since they are pretty strong.

 

[Exoskelos]

I’m going to agree with D. tityus. Appears to be an L3. Based on size, their appearance, and them feeding on hardwood I’d be surprised if it wasn’t. Adult care is pretty simple. Keep them in a substrate of rotting hardwood (larva eat the sub) that is kept moist, anywhere from four to six inches worth (although I have seen people keep adults on shallower sub/larva in deeper). Might even want to put some plastic wrap over whatever you are using as an enclosure to keep the moisture levels a bit more constant. The adults feed on fruits (without the skin since their jaws can’t break through it), a mix of real maple syrup and water, or beetle jellies.
As to the enclosure, you’ll want a decent lid for the adults since they are pretty strong.

So care for the grubs is about the same as millipedes then. I've got them in 3 or 4 inches of the rotten wood/detritus I originally found them in, and they're in a plastic shoebox I normally use for millipede enclosure transfers, with the lid on. Will that work, and is an L3 larva right before it turns into a beetle, or does it get even bigger?

Kinda sad I only found the two grubs, after three hours of digging the core of a stump out, and two feet below ground level, nothing. Do they only lay a few eggs, or are the larvae normally deeper underground in the root base? They were about a foot down into the rotten wood, right next to each other, maybe three inches apart.

 

[lostbrane]

From what I know, that works just fine. There’s a lot of leeway. Right now, I’m keeping a D. granti larva in a french press...

L3 is the last larval stage, before it pupates. I don’t know how old these grubs are so you might be seeing them pupate soon or it could be some months.

I do not know about egg distribution in the wild.

And in the event that it turns out to be some other rhinoceros beetle, at least the larvae are kept mostly the same, albeit with some slight tweaks.

 

[davehuth]

I agree that the Elytra you describe sound like D. tityus to me also, and luckily there's lots of information online about husbandry since they are such a gorgeous and popular beetle.

If you found them deep within the tree, especially if there was a hollow space around it, you could also look up the larvae and compare to Osmoderma. Generally Osmoderma would be a bit smaller than Dynastes, but I've dug a few L3 Osmoderma out of a tree that are half dollar size or a tad larger. Osmo's are also easy and fun to raise, and their lifecycle in captivity becomes a bit quicker than Dynastes.

Congrats while you wait for your surprise and update us here with photos once their pupae eclose!

 

[Exoskelos]

If you found them deep within the tree, especially if there was a hollow space around it, you could also look up the larvae and compare to Osmoderma. Generally Osmoderma would be a bit smaller than Dynastes, but I've dug a few L3 Osmoderma out of a tree that are half dollar size or a tad larger. Osmo's are also easy and fun to raise, and their lifecycle in captivity becomes a bit quicker than Dynastes.

I don't know about a hollow space, but the tree is about two and a half feet wide, and three inches all around it is still wood. The rest of the wood in the heart of the tree is just rotten into a reddish brown sawdust type soil. These grubs are definitely larger than a half dollar but not by much, I would guess similar in weight to a golf ball. I looked up the Osmoderma and I think these are most likely D. tityus. The elytra were definitely green, not brown. Plus I'm in the US, so unless it is invasive here, its unlikely to be those. I may take photographs of the tree I found them in when it stops raining here, I have no idea what kind of tree it is except its for sure deciduous.

 

[davehuth]

@lost

I don't know about a hollow space, but the tree is about two and a half feet wide, and three inches all around it is still wood. The rest of the wood in the heart of the tree is just rotten into a reddish brown sawdust type soil. These grubs are definitely larger than a half dollar but not by much, I would guess similar in weight to a golf ball.

@lostbrane probably has it right – your larvae do have those deeply grooved wrinkles of Dynastes. Maybe also take a look at some of the large Lucanus if they live in your area as well, just so you're familiar with a few genera when whatever you have reaches adulthood. But honestly much of their care is similar, so the surprise can be part of the fun. My limited (non-professional, just in it for the joy) experience has been that many of our North American beetles really take care of themselves given the right conditions, so it's easy to get hooked on them Best of luck.

 

[Exoskelos]

I've seen a lot of stag beetles around here, probably Lucanus, but I've also seen a huge green beetle (probably Dynastes tityus) once, it was like a baseball with wings. Of course I was probably only 8 or 9 years old at the time, memory has a tendency to exaggerate things.
I hope the grubs don't get as big as the one in this video, if this is even the same species of beetle. Is this something I should be expecting to see?

 

[lostbrane]

That is a Dynastes hercules. Impressive specimens to be sure. Your grub won’t get any larger than it is now.

 

[Exoskelos]

That is a Dynastes hercules. Impressive specimens to be sure. Your grub won’t get any larger than it is now.

Wonder if they can be obtained in the US, and if so where someone would go about getting them. But, on the other hand, me keeping a grub that big in the house would probably send my mom into a fit.

 

[lostbrane]

From my research, the answer is no, you cannot get them. I was originally going to try but found you couldn’t so I went with an American species instead.
Well, at the very least it would take a little while for it to get that big haha.

 

[Exoskelos]

From my research, the answer is no, you cannot get them. I was originally going to try but found you couldn’t so I went with an American species instead.
Well, at the very least it would take a little while for it to get that big haha.

Man, that's kinda depressing. Watching that video has me fully convinced that the pupa stage of that beetle was what caused H.R. Giger to have nightmares, and thats how the film Alien was created. "You see, it all started when I saw this beetle..."

 

[All About Arthropods]

Wonder if they can be obtained in the US, and if so where someone would go about getting them. But, on the other hand, me keeping a grub that big in the house would probably send my mom into a fit.

A few people have them, but they are not able to be kept legally in the U.S without a permit as of yet.

 

[Exoskelos]

A few people have them, but they are not able to be kept legally in the U.S without a permit as of yet.

Darn. I'll just file that under "pets I can never get", along with African land snails, various millipede species, ant queens, certain snake species, and velociraptors.

 

[All About Arthropods]

Darn. I'll just file that under "pets I can never get", along with African land snails, various millipede species, ant queens, certain snake species, and velociraptors.

Probably for the best on those velociraptors.

 

[Smokehound714]

if the larvae walk on their backs using their setae, they're cotinis

 

[Exoskelos]

if the larvae walk on their backs using their setae, they're cotinis

These things are way too big for that. They kinda wobble a little bit then start digging down into the soil. Here's some better photos, and I'm going up to take a photo of where they were found.