Cabbage White strange life cycle

[Mike_Howles]

I have been watching some Cabbage White caterpillars munching their way through our Swede and Turnips. Once they have fattened themselves sufficiently they then climb the wall at the back of the house to the highest point. They then 'lay' some 'eggs' in a sort of cocoon. The caterpillars then shrivel and die on the concrete below.
I always thought that the caterpillar turned into a chrysalis and then to a butterfly but this behavior is different unless something else has has a hand in it.
Just want to know what is going on??

Mike

Here we see the big fat caterpillar climbing the wall:



Here it has 'laid its 'eggs'



Closeup of the 'eggs':



Another on 'on guard'



Finally the shrivelled remains on the concrete:

[poschiavanus]

These are parasitised, probably by the common (braconid) parasitic wasp Cotesia glomerulata. There's an old thread about them here.

[Jim Ford]

The caterpillars have been parasitised by an ichneumon wasp. The wasp lays its eggs in the caterpillar, which then hatch and eat the caterpillar from the inside. When the caterpillar goes to pupate, the ichneumon larvae leave it and pupate themselves.

I'll bet you're glad you're not a caterpillar now!

Here's an image I took of a wasp laying its eggs in the nest of a solitary bee:



Jim

[Mike_Howles]

I had an idea that it was the effects of a parasite, just wasn't absolutley sure.

Amazing things these, they can parasitise an insect without affecting the insects normal behaviour up until the point where the parasite 'hatches'.

For two insects of low intelligence this is a marvel of nature!!

Very clever indeed.

Thanks for the responses.

Mike