by Extrasense
What are they?
Cicadas are noisy, chunky insects with bright red-eyes. More than 3000 species exist and not all of them emerge every 17 or 13 years. Cicadas with this kind of lifespan are called periodical (Magicicada genus), and are among the most abundant herbivores of deciduous trees in North America. Periodical cicadas spent a tiny fraction of that time above ground. The rest of a periodical cicada’s life is spent underground as a nymph feeding on liquid sucked from plant roots.
How do they know when to emerge?
Nymphs count the years by detecting the uptick in fluid flowing through the roots they feed on that occurs during each year’s spring growing season. After 13 or 17 cycles, periodical cicadas wait for the soil temperature to reach around 64 degrees before digging their way back to the surface. By emerging all at once in densities of up to 1.5 million per acre, cicadas manage to overwhelm predators, who quickly get too full to take another bite of the buzzing buffet, so at this point they are free to go about their business of procreating the next generation.
Natural predators and diseases
Cicadas’ life ain’t that easy, they face many problems like eager predators from birds to foxes, thunderstorms and specially a terrifying parasitic fungus of their own, Massospora cicadina. This fungus infects periodical cicadas while they’re rooting around in the soil as nymphs and is the only known pathogen synchronized to the cicadas’ life cycles. This fungal infection modifies the cicadas in ways contrary to the cicadas’ interests. The infections cause distention and loss of the terminal abdominal segments, genitalia included, in both sexes. The infected cicadas tend to drag their abdomen on the ground or tree bark leaving a trail of spores that could potentially infect healthy cicadas and start the cycle all over again.
Sample images of the Cicada infected by the fungus.
If you'd like to help Extrasense keep track of the emergence of this insect please consider taking a picture of the cicada with our free web app: https://webapp.extrasense.co/
We'll be sharing the results of the data we collected
References:
Cooley, J., Marshall, D., & Hill, K. (2018). A specialized fungal parasite (Massospora cicadina) hijacks the sexual signals of periodical cicadas (Hemiptera: Cicadidae: Magicicada). Scientific Reports.
Fox, A., 2021. 14 Fun Facts About Cicadas. [online] Smithsonian Magazine. Available at <https://www.smithsonianmag.com/science-nature/14-fun-facts-about-cicadas-180977361/> [Accessed May 25th 2021].
Williams, K.S., Smith, K.G. and Stephen, F.M. (1993), Emergence of 13-Yr Periodical Cicadas (Cicadidae: Magicicada): Phenology, Mortality, and Predators Satiation. Ecology, 74: 1143-1152.
Yang, L. H., & Karban, R. (2019). The effects of pulsed fertilization and chronic herbivory by periodical cicadas on tree growth. Ecology, e02705. doi:10.1002/ecy.2705