What really emerges?

A few days later, late in the afternoon, I went back to the Blue Spotted Crow chrysalis featured yesterday, and was very glad I had brought my macro set up, as I photographed something I had never seen before; a butterfly is just one of the creatures that might end up emerging from a pupa.


Yes, pupa (and butterflies and caterpillars) frequently host parasitoids, which are insects that attack and destroy their hosts, sometimes eating them alive. Typically, like here, these are usually wasps, laying their own eggs inside a butterfly egg, caterpillar or pupa.

I understand that this is actually quite a frequent experience, and clearly a huge disappointment for those who like to rear butterflies.

And this brings us to our word for today - polyembryony.

Some wasps just lay one egg, but that egg can divide into many identical embryos, which is called polyembryony. So like here, a whole mass of wasps can emerge from a host. I must have counted at least 40 of these little guys climbing out and then rapidly flying away.

I was lucky to get three in this shot, as this was the only one that did not fly away immediately after it emerged, and then two more were popping out.

Trying to get a suitable depth of field on such a small subject, while balancing flash diffusion on this highly reflective surface, whilst trying to keep things sharp, and not to leave the wasps in shadows meant that this was probably the most technically difficult shot I have ever taken.