They’re back, we hope. Within a week or two, the nymphs may emerge from the ground where they have hibernated for 17 years, occasionally sipping on water and other nutrients from the roots of trees and shrubs which they pierce with their beaks. The nymphs emerge from the ground, hatch into adults and start their mating cycle. “They” are periodical cicadas, the ones that make that high-pitched harsh squealing sound that can get on your nerves on warm early summer days.
There are two types of cicadas on the island. There are four known species here that emerge and call annually. They may appear at any time from June to late September, and their annual numbers may vary. Each species has a slightly different call the male uses to attract the female; the female is silent.
All cicada species we have here are between an inch and two inches long, have widely-spaced compound eyes and clear wings that are held like a roof over the body.
The male has specialized organs for creating his mating calls. Unlike crickets and katydids which rub body parts together to make sound, male cicadas create sound by very rapidly vibrating complex thin membranes and thick rib-like structures known as timbals located at the base of their abdomens. Together with enlarged parts of the abdomen that act as resonance chambers, the vibrations of the timbals greatly amplify the sound, up to 100 decibels in some species. Cicadas are much more often heard than seen because they live most of their adult lives in the tops of trees.
Besides the annual cicadas, there are periodical cicadas. There are seven species of periodical cicadas in the U.S., all classified in the genus Magicicada. Three species emerge en masse every 17 years in the northern portions of the country, and four species emerge en masse every 13 years in the southern parts of the country. It is interesting that 17 and 13 are both prime numbers, perhaps making it more difficult for any predator or parasite to become established on the same cycle.
In Massachusetts, our periodical cicada has the scientific name Magicicada septendecim. Over a century ago, the appearances of periodical cicadas were broken down by year of appearance known as broods. A Roman numeral was assigned to each year of appearance, I to XVII for the 17-year cicadas. In some years, no periodical cicadas emerge anywhere, but the brood number is kept for each anniversary of appearance for each given brood.
Mass appearances occur because all adults of the same brood are developmentally synchronized. In some places the numbers of insects that all appear within a few days can be from 150,000 to 1.5 million per acre. Such numbers overwhelm any predator or parasite’s ability to damage the entire brood. A significant number of individuals usually will survive to mate and produce the next generation. However, it is possible for a brood to shrink or even disappear. Brood XI which formerly lived in western Massachusetts has not been recorded since 1954.
Here on the Vineyard, we know we have Brood VIII which lives primarily in West Tisbury, generally between the village and the airport. It emerged and was mentioned in the Vineyard Gazette in 1917, 1934, 1951, 1968, 1985, and 2002. It is next expected in 2019. Otherwise, this brood is known from eastern Ohio, western Pennsylvania, and northern New Jersey.
We hope we also can find Brood XIV on the Island this year. We know it occurs on Long Island and commonly on Cape Cod, but it has not so far been recorded here.
Its original distribution probably included most of the coastal plain between Long Island and the Cape before the sea rose about 5,000 years ago to create the Vineyard, so it is likely to have been here in the past. Brood XIV’s last emergence on the Cape was in 1991 so it should be looked for here this year.
Early signs of pre-emergence nymph activity have already been detected on the Cape, but because we have a slightly colder climate which delays the emergence of many insects, adult cicadas may not be found or heard here until early or mid-June.
Please be on the watch for these fascinating insects. If you hear a concentration of cicada songs in any one area, please get in touch with me or the folks at the Felix Neck Wildlife Sanctuary. We would very much like to document the location and obtain specimens for genetic research being conducted by an entomological researcher who has done cicada surveys here in the past.