Fig. 1.

Interactions between insects and resident microbiota. (a) Gut microbiota of Drosophila melanogaster, an open system in which both the larval and adult stages gain microorganisms from the environment and previous life stages.(b) Gut microbiota of the mosquito, comparable to Drosophila, except that the microbiota is not retained in the pupal stage. (c) Intracellular bacteria in the aphid, an example of a bacteriocyte symbiosis (see text) in which the microorganisms are transmitted vertically to the female ovaries and inserted into the developing embryo; aphids have no pupal stage and summer generations (depicted) are viviparous. Black arrows, insect life stages; orange arrows, transmission of bacteria across life stages; green arrows, acquisition of microorganisms from the environment. [Figure prepared by S. Villareal and S. Franzenburg]