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Page 2 Working with Nasonia Nasonia vitripennis is a small parasitic wasp that is involved in a symbiotic relationship with a host organism known as Sarcophaga bullata, or a flesh fly. More specifically, Nasonia is a "parasitoid", which is a parasite that completely destroys its host. By interrupting the life cycle of Sarcophaga, Nasonia is able to use its host for nutrition and shelter. I. Sarcophaga Life Cycle The Sarcophaga host, which is harmless to humans, is associated with animal carcasses. A non-virgin female Sarcophaga will lay a large number of eggs on a carcass. The eggs rapidly develop into larvae (maggots), which will feed on the dead animal tissue. The larvae infest the carcass for nine to ten days before they wander into the soil surrounding the carcass in search of a dry place to pupate. Pupation involves the development of a protective "shell" or casing around the body of the Sarcophaga. Within the casing, a pupa develops into an adult fly in another nine to ten days (figure 1). As stated earlier, the parasitic Nasonia is capable of interrupting the Sarcophaga life cycle. An adult female Nasonia will lay her eggs within the Sarcophaga pupal casing. This provides a well-protected, nutrient-rich environment for developing Nasonia as they feed on the tender Sarcophaga pupa. The environment within the Sarcophaga pupal casing creates ideal conditions for the completion of the Nasonia life cycle. II. Nasonia Life Cycle Nasonia have a relatively short life cycle depending on environmental temperatures and exposure to a light source (figure 2). A female Nasonia lays her eggs in a Sarcophaga pupa by distending a long, thin structure, known as an ovipositor, from her abdomen. The female then deposits thirty to fifty eggs through the ovipositor into the pupal casing. The eggs develop into larvae within one or two days. The larvae then feed on the Sarcophaga pupa as a nutritional source. The larvae will continue to develop over the next eight to nine days, and then pupate, forming a protective casing around their bodies. There are three developmental stages of Nasonia pupae: "white", "black and white", and "black" stages, and each stage is more developed than the previous. Nasonia remain in the pupal stage for three to four days. In a process known as eclosion, "black" pupae will break free from their pupal cases as adults. These adults eventually emerge by chewing a hole through the host casing.