Can someone enlighten me.

First I am really pleased to be finding more nests of Peacock butterfly
caterpillars than for several years.

I have watched these swarms grow, but then they seem to drastically thin
out, leaving behind loads of shrivelled skins.  

Is this an indication that they have been parasitised or do they moult
skins before dispersing as they get bigger.

PS I found one nest of Small Tortoiseshell, again the first for several
years, and today I saw at least 4 pristine newly hatched individuals.  I
only recorded one on the reserve all of last year.

-- 
Regards from Bob Seago:  http://www.users.zetnet.co.uk/rjseago/