Cicadas are having a good year in our area
Of the several broods and subspecies of periodical Cicadas (Magicicada septendecim) in Frederick County, 2013 is a year of the second most prolific hatch of these insects.. Scientists have assigned Roman numerals to the the broods, the highest 17-year cicada numbers occurring with Brood X, which is on schedule for 2021. This year hosts Brood II of the 17-year cicadas bringing us a dramatic increase in numbers and decibel level.
Cicadas on occasion are mistakenly referred to as 17-year locusts, possibly due the large numbers observed by early settlers that seemed similar to Biblical stories of locusts. A locust is a different insect in the grasshopper family that can swarm when overcrowded. There are several broods of periodical cicadas that exist in our area, three 17-year broods and a 13-year brood plus annual cicadas and a few of the periodical varieties that are out of synch with their broods. Every year we hear locusts chirping in the summer and early fall. An annual locust is generally active June through October and has greenish highlighting on its wings. The periodical cicadas are generally active in May and June and have orange highlighting along the wings. Once the 17 year cicadas are gone this year, we will hearing the annual variety at a lower sound level into early fall.
The periodical cicadas feed as nymphs on roots for most of their life. Studies have shown that in the year prior to the large emergences, tree growth rings can be retarded as nymphs increase root feeding in anticipation of emergence in the spring. The loud chirping sound is made by the males to attract females. Females make a cut into small branches to lay eggs, causing branch ends to die off, or flag. The eggs hatch in about 2 months, and the nymphs drop to the ground to begin their underground lifecycle until the next 13 or 17 year emergence. The flagging of small tree branches, while unsightly, does not do long-term harm to trees. In big cicada years, some reduction in the production of mast such as acorns and seeds has been observed which also inhibits populations of small animals such as squirrels. Other animals including wild turkeys and birds that feed on cicadas have been observed to have population increases. Moles can have population increases in years prior to the large emergencies due to the increases in nymph size and activity underground.
The large numbers of adult cicadas, which may reach a million or more insects per acre, are believed to be a species survival strategy called predator satiation. The multitude of cicadas overwhelms the appetites of predator animals that feed on them, assuring many cicadas survive to reproduce. Science is still out on the reasons that the life cycles are prime numbers, 13 and 17 years, and why there are some variations, with insects emerging in low numbers at other times, the most common variation being 4 years before or after the normal brood year. In the north, 17 year broods are more common, with 13 year broods being mainly in the southern US. Cicadas do not bite and are considered harmless to humans and pets. Research indicates that Native Americans ate periodical cicadas, and some current cicada aficionados fry them like shrimp. Pets and wild animals eat them without harm. Of course, avoid eating cicadas from areas with pesticide applications.
Article by FCFCDB
Nature Notes for 5/26/2013