Philornis downsi

Philornis downsi is a species of fly (Diptera, Muscidae) that was first recorded in Trinidad and Brazil in the 1990s. It has been accidentally introduced to the Galapagos Islands (Ecuador). Adult P. downsi feed on fruit. Eggs are laid in bird nests and hatch into parasitic larvae which reside in the nest material and emerge at night to feed both internally and externally on the blood and flesh of developing nestlings. The parasite is causing significant mortality in Darwin's finch nestlings and threaten the survival of some rarer species such as the mangrove finch (Camarhynchus heliobates) and the medium tree finch (C. pauper). In order to protect the threatened finch populations, insecticide-laced cotton has been supplied as nesting material for the finches, with the results being highly successful in combating P. downsi infestations.