US Scientists Jump into the Study of Cicadas

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In a previous post, I made short notes about the Natural Reemergence of Cicada in the US. In a recent news article published in Nature, Sumeet Kilkarni writes that many US scientists are rushing to collect samples and observe an ecological phenomenon firsthand, as periodic cicadas begun to emerge in huge numbers across the southeastern and midwestern United States.

There’s an awful lot that we don’t know about these insects that spend most of their lives about 60 centimetres underground “in a little mud hole in the dirt”.

– Martha Weiss, an entomologist at Georgetown University in Washington DC (source: Nature)

Some scientists are interested in studying how these two cicada breeds interbreed, how the cicadas determine their timing of emergence from underground hibernation, and gaining additional insights into the rare fungus that infects these cicada breeds, among other topics.

The two emerging species of cicadas, Brood XIX and Brood XIII, have limited geographical overlap, with Brood XIX spanning a vast area from Maryland to Georgia in the southeast and from Iowa to Oklahoma in the Midwest, while Brood XIII covers northern Illinois, including Chicago.

Entomologist like Katie Dana from the University of Illinois Urbana-Champaign, is said to be interested in investigating their interactions and mating songs. She seeks to differentiate between the two species using DNA sequencing, as they are visually similar and interbreeding is possible but challenging to study in the field. Dana’s research involves observing their interactions and collecting samples for later DNA analysis, anticipating numerous graduate projects resulting from her efforts.

The other areas of research that scientists are interested in seek to answer the question, ‘how do cicadas keep track of time?‘ for their emergence from underground.

Periodical cicadas, upon emerging above ground, are said to engage in a loud and frenzied mating season, followed by females laying eggs in tree branches. After hatching, the white nymphs fall to the ground, burrowing into the soil to feed on tree roots for sustenance over prime-numbered stretches of years.

Scientists believe these cycles help them avoid synchronization with predators. However, how cicadas precisely determine whether 13 or 17 years have elapsed underground remains a mystery. Researchers hypothesize that epigenetics, particularly methyl groups, may play a role in regulating their internal clocks. Katie Dana and Chris Simon, an evolutionary biologist and entomologist at the University of Connecticut, are planning to collect samples this year to test this theory.

Sierra Raglin, a soil microbial ecologist at the University of Illinois Urbana-Champaign, is said to be interested to locate and collect fungus-infected cicadas this year, as well as look for spores in the nearby soil. “The soil and its microbiome haven’t been studied much in this context”.

It will be interesting to discover how much these entomologists capitalize on these unique opportunities to learn, document, and address their burning questions about these cicadas.