Persistence of Bacteria in the Developmental Stages of the Housefly

Abstract

Summary 1. Starvation experiments support the conclusion that the more than 90% decline in the number of bacteria in prepupae, as compared with mature maggots, is the result of a cessation of feeding and of continued elimination. 2. There is little likelihood of routine systemic invasion by the intestinal flora since, in the majority of maggots and prepupae, the hemolymph is sterile. Fat and tracheae are likewise sterile. 3. The hindgut of the prepupa typically harbors more bacteria than the midgut. 4. Dissections of pupae provide evidence for the translocation of the intestinal flora of the prepupa to the inner surface of the puparium, the molting membrane, and the surface of the pupa. The pupal gut retains very few organisms. 5. The fly emerges with a count near 102 from a puparium containing about 105 bacteria.