Biology and behavior of Microdon piperi in the Pacific Northwest (Diptera: Syrphidae)

A 15 year study of Microdon piperi Knab shows that it is one of the more common species of Microdon living in the wet forest habitat of the Pacific Northwest. The life cycle of this species is similar to that reported for other northern species, with adult flies emerging from puparia in ant nests during the spring from April to June. Mating occurs shortly after emergence, and the female deposits eggs in or near host ant nests. The larvae develop in the ant nest during the summer and overwinter deep within the nest as mature third instars. The principal host of M. piperi is Camponotus modoc, although it is found with several other species of Camponotus. The larvae mimic ant brood, their sole food source, and the life cycle of the fly is synchronized with the brood cycles of its host. These inquilines have virtually no impact on carpenter ant colonies and are not important population regulators.