Wolbachia in Butterflies

Wolbachia is a parasite found to infect Arthropod species around the world. The definition of Arthropod is an invertebrate animal having an exoskeleton, jointed appendages and segmented body.

Sixty percent of the arthropods hosting species are insects, one of which is the butterfly.

It is the organs in the butterflies that are infected. This bacteria is known, however, to infect primarily the male and female sex organs altering their reproductive capabilities...

Females can reproduce without fertilization from males.
Females can pass the infection to the next generation through the eggs she lays. The above picture is an infected embryo.
In males the bacteria can convert them into females or infertile pseudo-females.
If a male in infected by the bacteria where his sex is not changed he has an inability to reproduce with uninfected females.
Males during the larva stage are killed by this invader.

This bacteria is known as a male-killer

Discovered in 1924 by S. Burt Wolbach and Marshall Hertig in a mosquito species, studies have continued where conclusions were made and retracted too.

For example, It has been believed that this can be a form of natural selection. In some studies the male populations reduced drastically where females out-numbered males by as much as 100 to 1. In time with the progression of new generations the male population of certain species afflicted in these studies came back.

Interestingly it has been noted that some species carry the bacteria in their bodies and have become dependent on it to reproduce.