Blowfly Strike

Blowfly strike in the UK results in the opportunistic invasion of living tissues by the larvae of Lucilia sericata (greenbottles), Phormia terrae-novae (blackbottles) and Calliphora erythrocephala (bluebottles). Unlike the situation for sheep scab and lice, most of the blowfly lifecycle occurs off the sheep and adult flies can travel large distances without recognising farm boundaries. Adult female flies deposit eggs on dead animals or soiled fleeces. Eggs hatch into first stage larvae within about 12 hours. These larvae feed on tissue, grow and moult twice, becoming mature maggots in 3 to 10 days, depending on temperature and humidity. Third stage maggots then drop to the ground and pupate, mature flies emerging between May and September after 3 to 7 days. Flies over-winter in the soil as pupae, and emerge as soil temperatures rise during the spring. Blowfly populations are greatest during the summer months. The entire life cycle from egg to adult can occur in less than 10 days.

Primary flies including greenbottles and blackbottles can initiate strike on living sheep, while secondary flies including bluebottles only attack areas which are already struck or damaged. Maggots are active and voracious, causing skin and muscle liquefaction as they develop attracting secondary blowflies. Toxins released by decomposing tissues and ammonia secreted by the maggots are absorbed through the lesions into the sheep's blood, causing systemic illness which can cause death.

Read more