Help indentifying larval instar (D tityus)

[PowerHobo]

IDing larval instars is still pretty foreign to me. L1 especially messes with me now that I have hatchling D tityus, as their head capsule seems to grow several times its original size during the first week or two, and I've been under the impression that the head capsule size should be a constant during each instar (except immediately after a molt).

I checked on this bitey brat this morning, and it's much larger than last time I checked. Unfortunately, I did not previously measure its head, but currently the head capsule is measuring approximately 6.09mm wide. It's about 4-5 weeks since hatching.

Is L2 a safe conclusion here? Is there some general guideline to head capsule sizes at each instar?

 

[Garin]

That's really interesting that the head capsule is growing during L1. I have never seen that. But then again, I don't really measure it. I just can tell that all the L1 head capsules are "about" the same size. There is quite a noticeable size difference in the head capsule from L1 to L2 and L3.

In your picture, my vote would definitely be L2. The head capsule on L1's are very small. Usually only a few mm.

 

[Beetleben]

Given the time that passed from hatching, and the head capsule to body ratio, I would also opt for L2 (5-6mm sounds about right for that species in L2).

I am very surprised to hear that you think L1 head capsules are growing, which technically they should not be able to, given that they are made out of chitin and once hardened, cannot grow any more. maybe it is the change from L1 to L2 which normally happens quite quickly after hatching.

Cheers

Ben

 

[PowerHobo]

Thanks, guys. That's what I thought, but confirmation from people who know more is always nice.

I definitely know the only time head capsules should change is at a molt, and maybe it's just that the larvae come out of the egg so very tiny and their bodies grow so quickly that it's given me the illusion of head capsule growth during L1.

 

[Pewrune]

Usually, when you see a larvae with a head almost as wide as the body, it means it just molted. Unless theres no food and they are super skinny.

 

[Spyro]

Is there a good reference somewhere for the size of the head capsules during L1,L2,L3 for D. tityus?

 

[Bugboy3092]

The ultimate guide to breeding beetles (Orin Mcmonigle, aka dynastes on this forum) has an in depth section on breeding D. Tityus, and has size references for identifying larval instars.

 

[Spyro]

Ok, maybe I am missing it. I have just gone page by page through the The Ultimate Guide To Breeding Beetles, Coleoptera Laboratory Culture Methods by Orin MCMonigle and didn't see a single entry regarding the size references for identifying larval instars for D. tityus. Can you tell me a page number???

 

[Bugboy3092]

Ok, so apparently I was wrong, and theres no section on that (idk why I thought there was) but its pretty easy to tell. I think L1s have head capsules only a few millimeters wide, Im pretty sure L2s have head capsules about 1/4 inch wide, while L3s can have head capsules up to a little under 1/2 inch. Of course, I could be wrong. Youll get used to seeing them and telling instantly what instar they are.