100's of 'zombie caterpillars'

[lattytatty]

We live in a reasonably rural village in Notts, have lived in our house for 3.5 years and have never witnessed what we have been, and still are seeing this last week.

After numerous google searches I realise what we have is a very large number of large cabbage white caterpillars which have been injected by a parasitic wasp. Today I have watched the larva exit from a caterpillar and set about weaving their silky sacks. There are numerous caterpillars already sat on their nest of eggs and so many more climbing the walls.

There are a number of things we don't understand!

1. Where are all the caterpillars coming from?
2. Why are they climbing the walls of our house/garage/summerhouse to lay their eggs (many are now forming chrysallis (typo) on our property too)?
3. Why are they not on leaves?
4. Is this normal behaviour?

Each caterpillar on it's nest seems to have what I believe to be the parasitic wasp next to it. I liken it to something similar to a flying ant. Is this what the eggs will hatch into?

We must have cleared getting on for 200 caterpillars from our property already in just under a week, and still they keep climbing the walls.

If this is normal? How long can we expect it to carry on for?

I hope this makes sense to someone and you can give me some more information. Thanks in anticipation.

[jaguarondi]

Most caterpillars don't pupate on the plant where they fed. The transformation from larval to adult stage via pupa is a fairly drastic one with lots of inherent risk (pupae can't run away from predators). Therefore they generally choose quiet and sheltered places to pupate. Some caterpillars pupate in the soil. Those that do pupate on plants mostly wrap themselves up in lots of silk for protection.

[charlieb]

Ditto what jaguarondi said, but to add parasitized caterpillars tend to exhibit different/altered behaviour - in some cases making themselves highly visible (in my experience caterpillars you see will be parasitized, those you have to actively search for won't be)

Originally Posted by lattytatty

Each caterpillar on it's nest seems to have what I believe to be the parasitic wasp next to it. I liken it to something similar to a flying ant. Is this what the eggs will hatch into?

That sounds more like a (second) parasite that will parasitize the caterpillars parasites (if that makes sense!)

Have a read of this thread... Caterpillar and weird eggs ID??

It's been a good year for lots of insects, both lepiodoptera and their parasites