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hello everyone. For a couple of years now i have noticed that most of the cabbage white chrysalis on my house have a tiny hole in them and are full of minute flies. Can anyone tell me what species these flies are and how they get there. Many thanks

I notice that no one has replied! I am aware of wasps that lay eggs into the caterpillars of Large Whites, but I think they emerge while it is still a caterpillar.
I had some Small White chrysalises on the house a couple of years ago and I saw small black wasps taking an interest in them. Some of the chrysalises didn't eclose and later I found small round holes on them, so presumably the wasps had laid eggs in them and this is where the next generation had emerged.
Sorry I can't help with your flies, but I am sure you will find information via Google.

Hi Allyson,

I don't claim to be an expert on this subject, but I suspect that the flies are probobly small parasitic wasps (generally described as gregarious pupal endoparasitoid wasps). There are so many species that it is often very difficult to pin down an exact name, but here is a link to a site I found whilst researching the subject. http://pk-photography.blogspot.co.uk/20 ... parum.html . There are flies which aslo parasitize butterfly pupae, but these tend to be relatively larger.

Interestingly, some of these species of wasp are used as a biological control against butterfly pests such as Cabbage Whites.

Vince

Vince Massimo wrote:
Interestingly, some of these species of wasp are used as a biological control against butterfly pests such as Cabbage Whites.

That is interesting, Vince. I never knew that.