Camponotus vagus and Phoridae "ant-decapitating fly"

Description:

Thanks to the team and users of www.diptera.info for this first identification.Order=diptera Family=phoridae Genus=(Microselia OR Pseudacteon), hard to go further because I haven't got photos with good resolution.This is a plastic cap filled with water and sugar.I used this system to concentrate many workers of C.vagus so to attract the small fly that you can see in the middle of the cap.The critter is a Diptera of the Phoridae family, also known as "ant-decapitating fly".It is attracted by large number of busy workers and after following one for a while it perches on the abdomen (it normally prefers the lower side) and then lays its egg(s).The reaction of the worker is to go mad and try to remove it with the legs or the jaws. The closest workers get normally alarmed by this behaviour.I've noticed that the colonies heavily affected by this fly are affected by the CBPV "Chronic bee paralysis virus" as well, but I don't know if there are relations since the CBPV is known to be carried by mites (anyway I've never spotted mites on a C.vagus).When a colony is infected there are many dead workers around the nest, they lay in a unusual posture and if touched they easily lose the head.Tuscany, Italy