Blue bottle flies, Calliphora vomitoria, are active as soon as temperatures warm in the spring. They visit early spring flowers feeding on nectar. Blue bottle flies can be effective pollinators. Note the pollen attached to the hairs of the fly visiting a boxwood shrub.
Blue bottle flies lay their eggs on the carcasses of dead animals, which can be found at any time of the year. Larval development occurs only at temperatures above 50 F.