In a previous episode, we described the bizarre strategy called predator satiation used by periodical cicadas to overwhelm hordes of hungry predators intent on filling their bellies with these nutritious insects. The long life span may also enable periodical cicadas to elude short-lived predators that simply cannot wait 13 or 17 years for their next meal. Ahhh, but there is one patient nemesis of periodical cicadas that has evolved a diabolical plan for making the most of the cicada bounty. Beneath the trees where cicadas spend their youth sipping sap, spores of the fungal pathogen Massospora cicadina lay in wait for 17 years.
During April and May as cicada nymphs prepare for their escape from the earth, resting spores of Massospora adhere to the exoskeletons of the subterranean cicadas. Compounds on the surface of the cicada send a signal to the spores that dinner is served and it is time to germinate. Like an invading army the fungus penetrates the skin of the cicada and multiplies turning the cicada into a fungus garden. Spores of Massospora are then released into the environment where a second, more sinister wave of infection takes place. At this stage of their cycle, thousands of newly molted adult cicadas populate the landscape to begin the courtship ritual. Ubiquitous spores of the fungus spewed from the nymphs adhere to the skin of adult cicadas, germinate, and begin to infect the airborne legions.
Despite missing most of its abdomen, this cicada continues to walk about cicada land, spreading the contagious fungus.
The infection sterilizes both male and female cicadas, but does nothing to quell the libido of sex-crazed the male cicada. Infected males continue to seek and attempt to mate with females despite their contagious infection. In a game of tit for tat, female cicadas infected with Massospora remain attractive to healthy males that soon become infected as they attempt to mate with the Massospora Marys of cicada land. At this point in time Massospora becomes a cicada STD and is transmitted from one cicada to another thereby increasing its numbers each day. In a short suspense, the infection turns the abdomen of the cicada into a buff-colored mass of fungus. Infected cicadas are flight capable and their peregrinations carry the fungus to new habitats as cicadas fly about. The fungus-laden abdomens of infected cicadas eventually drop off and inoculate the soil with the resting stage of Massospora that will await the return of the cicadas in 17 years. While the loss of an abdomen spells instant death for a human, this is not the case for a cicada. Throughout cicada land male and female Massospora zombies walk and fly about missing their abdomens, macabre reminders of a very clever fungus.
The wonderful articles by K. S. Williams and C. Simon “The ecology, behavior, and evolution of periodical cicadas” and “Flying salt shakers of death” by Angie Macias were used as a resources for this episode.
To view other recent episodes of Bug of the Week that explore Brood II, and other excellent websites dedicated to cicadas, please click on the following links: