Sicus ferrugineus (Thick-headed Fly)

Sicus ferrugineus is a Thick-headed Fly with a mainly reddish-brown or yellow-brown body. They have a yellow head that is quite large and inflated-looking, with a lump at the front, narrow cheeks and short brown antennae. Their eyes are large and reddish in colour. When resting, they usually fold their abdomen forward.

They inhabit hedgerows and flower meadows, feeding on nectar or pollen of various flowers, like thistles, ragworts, knapweeds, scabious and bramble and can be seen from May through to September.

Their larvae are endoparasites of bumble bees, like the red-tailed bumblebee, buff-tailed bumblebee, garden bumblebee and common carder bee. Female Sicus ferrugineus pounce on worker bumblebees and inject an egg into the bee abdomen, using their specialised ovipositor. The larvae feed internally on the bees, pupate and overwinter in their victims.

A widespread and fairly frequent species in Britain.