Massospora cicadina

Initial infection takes place while cicada nymphs dig their way to the surface of the soil before emerging as adults.[5][6] It is presumed that the emerging cicadas are infected by resting spores they encounter in the soil. In early stages of infection, hyphal bodies of the fungus are found in the host tissues. Later, Stage I infected adult cicadas produce haploid conidia, forming the asexual stage of the fungus.[4] Conidia produced by Stage I infected cicadas are capable of infecting other adult cicadas. There is no difference between the proportion of male to female nymphs being infected by spores in this stage.[7] In the early stages of Stage I infection, the infection is completely concealed inside the abdomen of the cicada. Some time before the death of the host, the rear segments of the abdomen fall off, revealing a white, chalky mass or "plug" of the fungus, which produces spores. Because of this method of spreading of Stage I spores, cicadas infected with M. cicadina have been referred to as "flying salt shakers of death". Infected cicadas are infertile.

Stage I infected cicadas are observed to spend more time walking around and dragging their abdomen, which may aid in spreading conidia that infect other cicadas. This behavioral change is thought to be the result of a fungal extended phenotype, the physical afflictions of the infected cicadas, or the general phenology of cicada life cycles.[5] Progression in male and female cicadas is similar, including the time elapsed before the abdominal segments fall off.[7] Stage I infected males respond to mating calls of both males and females and attract healthy males through flicking their wings, a behavior only observed in healthy females. This altered behavior aids in infection of healthy cicadas.[5] Stage I infected males also tolerate mounting from courting males, suggesting that M. cicadina alters insect sexual behavior to increase infection rates.[4]

The fruiting bodies of M. cicadina on Stage I infected adult cicadas, are observed to possess a substituted amphetamine alkaloid, cathinone.[8]

Cicadas that come into contact with conidia from an infected adult cicada contract Stage II infection. During Stage II infection, the fungus produces a different kind of spore: resting spores that have thick walls and are not directly infectious to adult cicadas. Instead, the resting spores lie dormant in soil and will infect the next generation of cicadas during their next 13 or 17 year emergence from the soil.[1]

The fungus renders both males and females sterile, though the insect may remain alive and mobile while discharging spores. Infected cicadas display some normal behavior such as sexual responsiveness, and even copulation between infected and healthy cicadas has been observed.[1] As cicada males form large chorus centers during mating, the infection rate of males with the resting spore stage is typically higher than infected females at this stage.[4] Conidia that fill the abdomens of infected males at this stage also alter the pitch of their mating call, resulting in them sounding smaller than they actually are to females, which may also contribute to the prevalence of higher infection rates in males than in females.[4]