March 1 - Philornis downsi

Philornis downsi (Diptera: Muscidae) is a parasitic fly, originally found in Trinidad and Tobago and recently introduced to the Galapagos Islands. Adult flies, which are non-parasitic, feed on decaying, organic matter, while larval instars are hematophagous parasites that feed on the blood and tissues of nestling and adult birds, including Darwin’s finches. The adult flies lay their eggs in the nares of nestlings and in the bottom of nests. Even if the nestlings survive, their nares (on their bills) can be permanently deformed. The picture seen here is of 3rd instar larvae. The maggots develop through 3 pupae stages before emerging as adults. They are implicated in the reduced reproductive success of Darwin’s finches, which are a conservation concern.

Contributed by Sarah Knutie.