ABSTRACT
Introduction It is generally assumed that insect sexes are genetically determined. In some insect species, however, sexes can be partially or completely reversed by nongenetic factors such as temperature. Notably, endosymbiotic microorganisms can affect the reproduction of their arthropod hosts in various ways, such as feminization or male killing. In two groups of lepidopteran insects (i.e., moths of the genus Ostrinia and the buttery Eurema hecabe), it has recently been discovered that sex reversal from male to female can be caused by endosymbiotic bacteria of the genus Wolbachia. In this chapter, we briey review the general mechanism of sex determination in insects and then describe the Wolbachia-induced sex reversal found in these two groups of lepidopteran insects. We discuss the mechanistic bases and evolutionary implications of these phenomena and attempt to integrate our knowledge of male killing and feminization, which have been recognized as distinct phenomena caused by endosymbionts.
