A Note on Cicadas

Cicada exuviae (i.e., molted exoskeleton)

After finding the molted exoskeleton of the cicada above while wandering Xandari’s forest paths, I decided to do a little digging on the bug. The cicada is a common, but amazing, species of insect. A “true bug” (Hemipteran), the cicada is easily recognized by its large size, prominent eyes, and strong, well-developed wings. Often, however, we will hear a cicada long before clapping eyes on one. Their song can reach 120 decibels in volume, sufficiently loud to deafen a human ear permanently if it were to produce its song close enough by. Interestingly, this sound is not produced in the same way as the songs of grasshoppers and crickets. Grasshoppers are stridulating insects, meaning that they produce their music by rubbing together their legs. Cicadas instead have a complex web of tissue below their abdomen that produces noise when the cicada flexes the muscles in the region. They can do this so quickly that the individual muscle contractions blend into a constant whirring sound. Another interesting fact concerning cicadas is their unusually long life cycles. Some species of Cicada (e.g., Magicicada) have life cycles as long as seventeen years, meaning that this amount time elapses from the cicada laying its eggs to the young hatching and making their way into the world. This long period of dormancy originated as a defense against the Cicada’s various enemies: none of its potential predators (praying mantis, etc.) can live long enough to predate the younger insects.

Here is a picture the live insect (source: Salon.com):

Source: salon.com

 

4 thoughts on “A Note on Cicadas

  1. Help me understand the last sentence. While cicadas are dormant, and predators die away before they the cicadas emerge, aren’t new predators also hatched that can eat the cicadas, when finally the cicadas emerge? Very enjoyable column – appreciate your sharing.

    • Thanks for the comment. I guess I should say, first, that not all species of cicadas have long dormancy periods; many hatch annually and are consequently predated by specifically evolved predators (like the Cicada killer). Those that have longer dormancy periods (13 or 17 years, Magicicadas) won’t necessarily avoid general predation, but the infrequency of their appearance means that fewer predators will be able to evolve in such a way as to target them specifically as a food source. A second, and more important, qualification is that the exact reasons for the specific number of years and the long duration of these cicada life cycles are not well understood. So, we’re back at square one!

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