#1
(First of all, apologies if it is not the right place. I ask here because it's the most expert entomology forum I know.)
My wife, a primary school teacher, raises V.cardui every couple years to show kids insect metamorphosis. They are commercial kits with larvae, net cage, artificial food. Usually everything goes OK, sometimes a caterpillar dies or a butterfly hatches with poor wings, but that's it.
This year, a malformed butterfly eclosed from the pupa. It has a poorly developed, black head, with no apparent trace of antennae, eyes or mouthparts. Yet it is alive and some trace of eyes could be present, since it apparently reacted to my smartphone flash when I tried to make a picture using it. Wings are also distorted because it fell shortly after eclosion, apparently -my wife found it upside-down on the floor of the cage and had to help her stand up. It's too weak to fly, but it can move.
I posted it on Facebook and a friend (who is a lecturer on Drosophila molecular biology at UC London) said it could be a genetic mutation, possibly Pax6. The odds seem astronomical to me, however. What else could have happened here? I tried to find descriptions of similar malformations in the literature, but to no avail.
#2
In case anyone is interested, here is another picture, from today at 12.
I contacted a biologist working on insect head development and asked me to bring the dried specimen for microscopic imaging. I have no experience at all in handling insect bodies. How do I dry/preserve it?
#3
That would be a weird one if it is a mutation, but I'm wondering whether the caterpillar's head capsule somehow got stuck on the end of the chrysalis during pupation, and slipped neatly over the butterfly's head on eclosion?
If you want to keep the specimen, I would suggest killing it in a freezer and then letting it air dry before packing lightly between tissue layers in a crush-proof box or tin.
#4
That seems a very interesting hypothesis! As far as I can see online, the head of the V.cardui caterpillar resembles closely the head of this butterfly. I did not think of it because I only saw the adults. Either what you say happened, or the head failed metamorphosis (is that even possible?)