the adzuki bean borer (Ostrinia scapulalis). Parthenogenesis is reproduction of infected females without males. Some scientists have suggested that parthenogenesis may always be attributable to the effects of Wolbachia. Though this is not the case for the marbled crayfish. An example of parthenogenesis induced by presence of Wolbachia are some species within the Trichogramma parasitoid wasp genus, which have evolved to procreate without males due to the presence of Wolbachia. Males are rare in this genus of wasp, possibly because many have been killed by that same strain of Wolbachia. Cytoplasmic incompatibility is the inability of Wolbachia-infected males to successfully reproduce with uninfected females or females infected with another Wolbachia strain. This reduces the reproductive success of those uninfected females and therefore promotes the infecting strain. In the cytoplasmic incompatibility mechanism, Wolbachia interferes with the parental chromosomes during the first mitotic divisions to the extent that they can no longer divide in synchrony. Effects of sexual differentiation in hosts Several host species, such as those within the genus Trichogramma, are so dependent on sexual differentiation of Wolbachia that they are unable to reproduce effectively without the bacteria in their bodies, and some might even be unable to survive uninfected. One study on infected woodlice showed the broods of infected organisms had a higher proportion of females than their uninfected counterparts. Wolbachia, especially Wolbachia-caused cytoplasmic incompatibility, may be important in promoting speciation. Wolbachia strains that distort the sex ratio may alter their host's pattern of sexual selection in nature, and also engender strong selection to prevent their action, leading to some of the fastest examples of natural selection in natural populations. The male killing and feminization effects of Wolbachia infections can also lead to speciation in their hosts. For example, populations of the pill woodlouse, Armadillidium vulgare which are exposed to the feminizing effects of Wolbachia, have been known to lose their female-determining chromosome. In these cases, only the presence of Wolbachia can cause an individual to develop into a female. Cryptic species of ground wētā (Hemiandrus maculifrons complex) are host to different lineages of Wolbachia which might explain their speciation without ecological or geographical separation. Fitness advantages by Wolbachia infections Wolbachia infection has been linked to viral resistance in Drosophila melanogaster, Drosophila simulans, and mosquito species. Flies, including mosquitoes, infected with the bacteria are more resistant to RNA viruses such as Drosophila C virus, norovirus, flock house virus, cricket paralysis