Tiny dark grey flies, only about 2mm long with hair-fringed wings, most prevalent in spring and summer near sewage works. Also known as Filter Flies or Owl Midges, their grubs perform a useful purpose because they break down organic material at sewage works.

REMEDY: Should adults fly indoors, use a flykiller aerosol. If the problem is severe, call in a specialist servicing company for treatment with insecticidal fog or commercial insecticide.