Peacock caterpillar question

[Newnettlesfan]

I recently noticed a large number of black caterpillars on a big patch of nettles behind my garden. They were large and have all gone now, hopefully into little cocoons.

There are several groups of baby caterpillars under tent webbing within the nettles, they appear rather dead and a bit shrivelled. Could they be dead? Resting? Would they have dried out in the recent strong sun?.

Or what could of killed them, doesn't appear to be any movement for a few days now

Really curios, am now very fond of these caterpillars and hope to see lots of butterflies...but not seen any yet

Thanks for any info

[Vince Massimo]

Hi Newnettlesfan and welcome to the site

The large caterpillars would hopefully now have found a safe site to pupate.

The smaller ones would usually be quite safe in their silk tent, which would protect them from the sun and rain and they can also feed from inside. Just prior to moulting their skins they will remain motionless (usually as a group) and will then emerge to form a new larger tent on fresher leaves. You may just be seeing the old discarded skins from a recent moult (together with a few dead individuals). There are however some viral diseases which can kill the majority of a colony, so I cannot rule that out at the moment. If you can get some photos I should be able to get a better idea of what is gong on. Otherwise, keep an eye on the colony and report any further observations.

In the meantime you can see an illustrated Peacock lifecycle here
viewtopic.php?f=37&t=6485

Vince

[Newnettlesfan]

Thankyou for your reply, I think maybe they are empty cases I have tried to attach photo showing one group at front right and one further back at left, not sure if anything will be clear enough so can always take another pic tomo.

Thanks

[Vince Massimo]

I'm afraid I can't see clearly enough at the moment. There are certainly some old webs and lots of old droppings and feeding damage. If you can get clearer shots of the front and rear groups, it would be very helpful.

Vince

[Newnettlesfan]

Hi Vince, this is the best close up I can get with my device, hope it helps.

Thanks for your link, that was amazing photos and so detailed, I've googled about them but haven't found a resource as good as that

[Vince Massimo]

Thanks for the photo, that's now a lot clearer and I think I can see what is happening.

Firstly, these are only larval skins, but I don't think they are all moulted ones. What I believe has also happened here is that some have been parasitised by a particular species of small wasp or fly. The eggs are either accidentally ingested by the caterpillar or injected directly into the body. One or more of the parasitic larvae hatch within the body of the caterpillar and consume it from the inside without killing it. After a while the parasitic maggots burst out of the body of the caterpillar, leaving a floppy but almost complete skin.

If you compare a cropped version of the lower part of your image to one showing confirmed parasitised larval skins, I think they are very similar in appearance. However some of the skins at the bottom of your image do look like moulted ones.

Peacock larvae parasited by Phobocampe confusa

Vince

EDIT: After inspecting a number of old Peacock larval webs today (23rd July) I have amended the above post to reflect my observations. Whilst it is difficult to be conclusive, I believe that most of the larval skins in your main image are likely to be moulted ones.