Parasitoids
The parasitoid fly Aplomya confinis (Fallén, 1820) of 7mm, from the family Tachinidae (Diptera), parasitizes caterpillars of different species from the family Lycaenidae. In this video this parasitoid parasitizes a caterpillar of the Common Blue (Polyommatus icarus). This tachinid glues its egg on the body of the caterpillar. In one day the larvae (maggot) penetrates the skin and develops inside the body of the caterpillar.
Identified by Dr. Hans-Peter Tschorsnig
Azuré commun 
Common Blue 
Fleeting wonders
Butterflies of France 
Matt's European Butterflies
Anything but common 
L'Ecaille Matrone 
Lépi'Net