By Will Dunham
WASHINGTON (Reuters) – Parts of the United States are about to experience a rare natural phenomenon with the simultaneous appearance of two giant adjacent periodical cicada species.
More than a trillion of these noisy insects are expected to pop out of the ground starting in April.
The two broods, one concentrated in the U.S. Midwestern states and the other concentrated in the South and Midwest with a small area of overlap in Illinois, occur together only every 221 years.
Here’s an explanation of what’s expected to happen during this “dual emergence.”
What is Cicada?
Cicadas are relatively large insects (2.5-5 cm) long, with robust bodies, bulging compound eyes and membranous wings. There are many different species of cicadas.
Using needle-like mouthparts, cicadas feed on plant sap called xylem, obtained from the roots of deciduous trees and shrubs. They spend most of their life cycle (years) underground as nymphs, feeding on roots and drinking xylem.
After emergence, adult males “sing” to attract females using special organs called tymbals in the first part of the abdomen. The pitch, tone, frequency, and volume of the song are specific to each genre. Cicadas live as adults for only a few weeks, then die after reproducing. Many birds and mammals eat cicadas.
How do PERIODIC AND ANNUAL Cicadas differ?
Among annual cicadas, some individuals occur in any given year. Depending on the species, they spend one to nine years underground as nymphs and do not have a synchronized emergence. Instead, they appear gradually.
Periodic cicadas have more specific and longer periods of time spent underground as nymphs – usually 13 years or 17 years – and a synchronized emergence. This means that all members of a given brood emerge in the same year, from late April to June, depending on their location. All periodic cicadas that appear together in a given year, sharing the same life cycle, are called broods, although any species may be part of different broods.
There are more than 3,000 species of cicadas worldwide, but only nine are periodic and seven of the genus Magicicada are found in North America. In India, a periodic species of the genus Chremistica occurs every four years, while in Fiji, a periodic species of the genus Raiataena occurs every eight years.
WHICH TWO PUPPIES ARE INCLUDED IN THIS YEAR’S DOUBLE RELEASE?
Brood XIII, which has a 17-year cycle, is mostly confined to northern Illinois, eastern Iowa, southern Wisconsin and a few counties in northwestern Indiana, according to entomologist Floyd Shockley of the Smithsonian Institution’s National Museum of Natural History in Washington. Brood XIII includes three species of Magicicada.
Brood According to states. Together, the two incubators cover parts of 17 states. Brood XIX includes four species of Magicicada.
These two cubs overlap only in a small area in central Illinois. They are close enough to have the potential for hybridization between offspring.
WHEN WILL THIS DUAL EMERGENCE APPEAR?
Periodical cicadas are expected to begin appearing in the southern parts of their geographical distribution from mid-April. Emergence continues northward until June. According to Shockley, there would easily be more than a trillion cicadas during this emergence, given that most broods produce local population numbers exceeding 1.5 million cicadas per acre (0.4 ha) in densely populated areas of their distribution.
What Do Cicadas Do When They Emerge?
Cicadas begin to emerge, mostly at night, when the soil warms to about 64 degrees Fahrenheit (17.8 degrees C), according to George Washington University entomologist John Lill. These nymphs crawl on any hard surface (tree trunks, fences, vegetation) and transform into adult winged cicadas.
After a few days, adults fly into the shade of the tree; Here males form loud “choruses” and call to females by vibrating their bells. Males have rather hollow abdomens that act as echo chambers to amplify their calls. Cicadas are among the loudest insects. Females attracted to a particular male’s call respond with wing movements that also produce sounds. The couples then mate.
According to Lill, after mating, female cicadas look for pencil-sized branches of trees and shrubs in sunny places to lay their eggs in slits they cut in the branches. These eggs develop for about six to seven weeks, after which the hatched nymphs drop to the ground and build nests to start the next generation of periodical cicadas.
WHEN WILL THIS BUG-TASTE EVENT HAPPEN NEXT?
These two cubs last appeared in the same year in 1803. The next time is set for 2245.
(Reporting by Will Dunham in Washington, Editing by Rosalba O’Brien)