The warble fly is a nasty parasite which really gets under the skin of Santa's reindeer. Hypoderma tarandi is a pest known to afflict most reindeer populations and it has a life cycle rather similar to the human bot fly. The adult flies lay eggs on the skin of reindeer, and hundreds of eggs can be found in the hide of a single deer. When the egg hatches, the maggot penetrates the skin and burrows under the subcutaneous layer where it proceeds to grow by feeding on host tissue. The maggot can grow up to 2.5 cm long (about an inch) and each deer can be infected with anything from 50 to 300 of such maggots, with some less fortunate individuals hosting 1000 fat maggots under their skin! Ouch -that's going to hurt when Santa hooks them up to their harnesses.
Contributed by Tommy Leung. Photo by Arne Nilssen.