Acherontia atropos cannibalism amongst caterpillars

Hello all, recently I've been noticing that amongst about 15 Death's head hawkmoth caterpillars there's been a recent bout of cannibalism between some of the late l5's and their earlier instar siblings ( mostly those preparing for a moult). I've seen them quite readily chewing up some of their younger counterparts and was wondering if there is a way to prevent it. Caterpillars are currently feeding well on a mix of privet, buddleia and jasmine.

Quote from Natalia

As already written, separate is an option. Otherwise, more space and more food if they are kept together. I am quite sure that if the caterpillar has the choice between food and conspecifics, it will choose the food. When the caterpillar is under feeding stress (not enough or good enough plant), I have observed cannibalism in this species.

Originally I'd pinned it down to it only happening in the rare cases when I'm unavailable to replenish foodplants but it just seems to be a casual thing they do without warning, you may be right about nutrition though since a lot of the privet and jasmine around me has been going a bit discoloured. It's also been manifesting itself as another issue amongst my silkmoths with a good few making loose cocoons for pupation ( or no cocoon at all) and small pupae. I've raised this species once before ( my current ones are descendants of a previous brood) with no such issue but that was earlier in the year with less caterpillars. I've started separating any of the smaller individuals but a lot of the smaller ones are getting ready for a moult and I don't want to disturb them. Appreciate the help from everyone here

Quote from avi

Hi

I saw it also with Acherontia styx, i started with 100 caterpilars and lots of them " disapeared". Now one was dead on the floor of the cage....

Interesting, cannibal caterpillars are something I've seen from noctuids and some tiger moths but hawkmoths are a new one for me. I suppose it explains why early instars are so defensive when bothered by siblings and why a lot of hawkmoths don't lay their eggs in big batches like some other species.

Quote from Natalia

Especially in the case of A. atropos, the immense amount of food plant, which is devoured until pupation, could also be decisive for the individually laid eggs. They are also site-loyal, so in my opinion the single egg-laying makes total sense.

I have also noticed cannibalistic behaviour in Smerinthus ocellata. Similar to what you have described, Mothdragon, the victims are mostly caterpillars that are resting before moulting. Whereby I assume that atropos has the clear intention of wanting to eat. In the case of ocellata, there could be a risk of confusion: I have observed that the anal horn is nibbled and the caterpillar usually survives. But a caterpillar in moulting rest of ocellata is also more able to defend itself than in atropos. They lash out very fast and hard.

I would be interested in your thoughts on this. Intentional or accidental? Or an attempt to eliminate a food competitor? After all, could atropos really feed on a conspecific to such an extent that it survives? (If no other food is available?)

So so, I would therefore recommend never keeping too many Sphingidae in too small a space.

From what I can tell it seems predatory, I watched one caterpillar actively crawl onto the mesh ( ignoring food plant) and start biting into an l3 caterpillar getting ready to moult. It's started to become a somewhat frequent thing towards any smaller individuals but all caterpillars that are the same size are completely peaceful with one another. Previously I've seen tail horns being bitten off and have pitted it to accidental consumption but now it's seeming a bit more predatory in intent. I'll be curious in seeing if it's the same when my Sphinx ligustri pupae hatch out and hopefully lay some eggs.