Sunday, March 31, 2024

Cicadas are Coming

This spring (late April and early May) the 17-year Brood XIII Cicadas will emerge in Northern Illinois, while the 13-year Brood XIX Cicadas will emerge in parts of Southeastern United States including parts of Virginia, but probably not more than a few stragglers in Northern Virginia.   Many people know periodical cicadas by the name "17-year locusts," but they are not the locusts of the bible. Those were a type of migrating grasshopper. However, if you live in the area of this year’s emergences , it may indeed feel like a plague for a few weeks. This is a big one, it is expected that this combined emergence will bring a trillion or more Cicadas.

However, counts of Cicadas are only estimates based on a very old data point.  The oft-quoted figure of densities that can exceed a million per acre comes from a census taken during the 1956 emergence of Brood XIII in Raccoon Grove, IL (Dybas and Davis 1962). Ironically, Brood XIII appears to have gone extinct in Raccoon Grove in the years since 1956 (Cooley et al. 2016). If the estimate of a million cicadas per acre is valid, then more than a trillions of cicadas will emerge in 2024 when Cicadas will emerge from Maryland to Oklahoma, Illinois to Alabama. It is not common to have a dual emergence between Broods XIII and XIX. They occur once every 221 years and the last time these two broods emerged together was in 1803 when Thomas Jefferson was President of the United States.

When they emerge in mass, you can report periodical cicadas using the Cicada Safari App, available on the Google Play Store or the Apple Store.  This will help scientists map the full extent of Brood XIII and XIX then we can really know the full extent of the Broods. If it does not feel like you are being inundated and you only see a few cicadas, they are probably stragglers from other broods and should not be reported. Otherwise, users can submit video and photos of periodical cicadas to the app. Once verified, they will be added to an online map. The app greatly assists in Cicada research.

from University of Conn

In late April and early May, Cicadas, probably both Magicicada septendecim and Magicicada cassinii will emerge from the soil and climb onto nearby vegetation and other vertical surfaces. They then molt to the winged adult stage. The emergence is tightly synchronized, with most adults appearing within a few nights. Adult cicadas live for only two to four weeks. When the 17-year periodical cicadas emerge the density can be shocking and noisy. It is common to have tens to hundreds of thousands of periodical cicadas per acre, but there are records of up to a million and a half periodical cicadas in an acre. This is far beyond the density of most other Cicada species and half of the Cicadas are “singing.” Male cicadas sing quite loudly by vibrating membranes on the sides of their abdominal segment. Male songs and choruses are a courtship ritual to attract females for mating. 

The males’ choruses have been known to drive people to distraction-stay inside with the windows closed if needed. However, for most people, the droning song of the cicada is nothing more than a slight annoyance. To me the “song” sounds like wind on a cell phone connection, but you can listen to the actual chorus on this U-Tube video from Storyful Viral. Most people are more familiar with the dogday cicada that is prevalent annually in mid-summer. Their song is later in the summer and not as persistent.

The 17 year or 13-year periodical cicada is black, with red eyes and orange legs. “Adults have clear wings with distinctive orange veins. When viewed from the front the wings form an inverted "V" and meet at the top like a roof.” After mating, females lay their eggs in narrow young twigs slicing into the wood and depositing up to 400 eggs in total for each female in 40 to 50 locations each. It is the egg laying that does most of the damage associated with periodical cicadas. Cicada eggs remain in the twigs for six to ten weeks before hatching. The nymphs do not feed on the twigs and all but the youngest trees will recover.


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