File:Cluster Fly (Pollenia angustigena) male (26104405983).jpg

I found this fly in my garden (Ipswich, Suffolk) on 1 April 2016. ID confirmed by Olga Retka. These flies do not pose a health risk as they stay away from human food. Instead they lay their eggs near earthworms so that their babies can infest the worms. When the maggots turn into adults in the autumn they seek shelter to hibernate. Unfortunately they sometimes cause a nuisance by sheltering indoors in quite large numbers, in clusters I suppose - hence their common name. The images presented in the collage are those needed to identify the species using Steven Falk's excellent draft key to British Calliphoridae and Rhinophoridae, plus some microscopy inspired by a paper entitled Cluster Flies of North America by Adam Jewiss-Gaines et al.