Microsporidia

The discovery of microsporidia was a landmark in early insect pathology studies. Microsporidia are obligate intracellular parasites that have refined "the art of living together" with their hosts by minimizing damage in order to achieve optimum reproduction and transmission to new hosts. The assumption that the number of described microsporidia species is a minute portion of those actually existing was corroborated by a study in which 22 novel species were isolated from soil, sand, and compost. Microsporidia can be transmitted horizontally from one host individual to another, or vertically from parent to offspring. Microsporidia that partially or completely depend on vertical transmission need to be of relatively low virulence in order to be successfully transmitted to the next host generation. Vertical transmission should be an important trait supporting the persistence of a microsporidium in the host population, especially during the periods of low host density that are known to occur with this univoltine outbreak species.