Thursday, May 25, 2017

The Cicadas are Emerging Early

Cicadas, probably Magicicada septendecim and Magicicada cassinii have arrived four years early in greater Washington DC metropolitan area. This year precursors to the cicada Brood X due in 2021 are emerging early and may continue to  emerge in the next couple of weeks around D.C. in Delaware, Maryland, Pennsylvania, Virginia, and West Virginia as well in other areas of Brood X. In Virginia there are seventeen broods of the 17-year cicada and thirteen broods of the 13-year cicada. Every year they will emerge somewhere in the state, but Brood X due in 2021 is one of the largest.  There may be a significant enough number of early emerges this year to qualify as a new brood and you can help scientists monitor this.  

Reports of cicadas have been widespread and this might be an acceleration event. Periodical cicada accelerations occur when a significant group of an established brood emerge in years ahead of the main brood, and sometimes the accelerated group are able to reproduce and create what is essentially a new brood. This is believed to be how Brood VI was formed. W.T. Davis documented accelerations of cicada populations back in the 1800s, which was reported in the 1898 report “The Periodical Cicada. An Account Of Cicada Septendecim, Its Natural Enemies And The Means Of Preventing Its Injury.

Cicadas that emerge either ahead or behind schedule are called “stragglers.” In terms of cicadas, scientists and naturalists have been using the term “straggler” for over a century, so it has stuck despite the common meaning of straggler as behind the group. Typically 17-year periodical cicadas emerge 4 years early or one year late. Climate or weather can impact a cicada cycle and there is a natural tendency to accelerate when population density becomes too great. If there is a high density of them underground, vying for limited resources, some might emerge early or a year after the main Brood.

Climate variations can also trigger periodical cicadas to emerge ahead of their brood. Periodical cicadas take cues from the seasonal cycles of their host trees. An unusual climate event, like a hot fall or winter, might cause trees to signal cicadas that additional years have passed, and cause them to shift to emerge early. Metropolitan areas like Washington D.C., or “heat islands” can often be much hotter than surrounding rural areas due to population density. The effects of living within a heat island may have disrupted the seasonal cycles of the cicadas’s host trees, and also the cicadas.

You will know the cicadas by their song, which to me sounds like wind on a cell phone connection, but you can listen to the actual chorus on the u-Tube video above. 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. If you hear the cicadas chorus report the finding to

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. The newly hatched, ant-like nymphs fall to the ground where they burrow 6 to 18 inches underground to feed on roots. Mature trees and shrubs usually survive even dense emergences of cicadas without long term damage, but in the summer of a large emergence many deciduous trees turn brown due to the breakage and death of peripheral twigs caused by the females laying their eggs and the emergence of the nymphs. Nonetheless, only young trees are usually permanently damaged and that is because so much of these trees are small twigs and branches.

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