PERIODICA CICADAS (Magicicada) ARE COMING TO RIVERWOODS!

How many different cicadas are there?
There are about 2,000 species of cicadas worldwide – but less than 100 species can be found in North America.

Why do we see cicadas every year?
Most cicadas have multiple-year life cycles (2-8 years), but they are not synchronized. Every year, some of these non-synchronized cicadas emerge in the summer – they are called dog-day, or annual, cicadas. A few species, called “periodical cicadas”-- only found in North America -- have very long life cycles and their life cycles are synchronized. They all emerge in the same year and all remain in the ground for 13 or 17 years until they emerge again. There are 4 species of periodical cicadas in North America with 13-year life cycles, and 3 species with 17-year life cycles. Once in a while, periodical cicadas emerge “off-schedule”. So any given year, we may see annual cicadas, or we may see both annual and periodical cicadas…including some of the “off-schedule” stragglers.

Periodical cicada timetables
Periodical cicadas appear in different years in different areas of the country.
Each group of cicadas on a particular timetable is called a “brood”. There are 3 broods of 13-year cicadas, 2 of them in Illinois. The next brood of 13-year cicadas in Illinois will emerge in 2011. There are 12 broods of 17-year locusts -- 3 different broods live in Illinois. You may have noticed 17-year cicadas in 2004. You will certainly see them this year. And in 2014, a brood will emerge here, too.

Get ready for the biggest emergence of 17-year cicadas in North America!
The largest brood is emerging here now. In a 1956 study done in forested floodplains near Chicago – just like Riverwoods – 1.5 million cicadas per acre were counted! In 1990, people were shoveling them off their driveways!

Life cycle of the Periodical Cicada

Nymphs – 17 years underground Cicada juveniles are called nymphs. They live underground, sucking on the juicy roots of trees for food. In early spring of the year they emerge, the nymphs dig exit tunnels to the surface. You can see 1/2 inch diameter holes or little chimney-like mud turrets throughout Riverwoods. Usually at night, when the soil temperature (and the nymph body) reaches over 64 degrees F, the nymphs crawl out of their holes and up a tree.

Adults – 5-6 weeks The nymphs cling to the tree trunk and shed their exoskeletons. Soft, pinkish white adults emerge. In a few hours, the adults harden and darken. The adult stage lasts five to six weeks.

Climbing the trees The adult 17-year locusts have bodies that are about 1.5 inches long. They are mostly black on top, reddish brown beneath, with red-orange legs and wing veins. They have bright red eyes. Adults leave the nymph exoskeletons clinging to the tree trunk and walk up to the top of the trees.

The mating game Males sing to attract the females. Females flick their wings in response, but they do not sing. Scientists identify the various species of cicadas by their song. With millions emerging at one time, the chorus of “songs” will be a very loud drone this year! Cicadas flying around, seemingly in any and all directions, are looking for mates. During this time, they may eat by sucking sap from small twigs and branches, but they do not eat leaves.

Doing little damage / eggs - 6-7 weeks The females make 40-50 slits in small twigs, branches and stems, inserting up to 400 eggs. The slits weaken the branches, so if the plant is very young, this may do some damage. Older trees and shrubs will be pruned, but are unlikely to be harmed – in fact, in forests, this natural pruning may be beneficial.

Completing the cycle In six to seven weeks, the eggs hatch. The nymphs that hatch look like pale ants with large front legs. They drop to the ground and dig into the earth. The little nymphs attach themselves to roots and begin 17 years of life underground. They will go through 8 stages, feeding on roots, molting and growing larger, until they are ready to emerge again.

Are the cidadas harmful? Cicadas do not sting, bite or carry diseases. They do not harm the trees when underground, sucking on the roots. They do not damage large trees or shrubs, though they may do some pruning at the tips of branches. Periodical cicadas may harm small young shrubs and trees. Protect them with netting during the 5-6 week adult stage.

Do they have predators? All kinds of animals eat the cicadas: birds, spiders, mites, snakes, dogs… people can eat them, too! There is even a large black and yellow parasitic wasp called a cicada killer that paralyzes the insect, drags it to a burrow, uses the cicada’s body as an egg repository and then, food for the larva that hatch. But there are so many periodical cicadas, predators cannot reduce the population.

Enjoy the show!
We will be living with the largest population of cicadas that emerge at one time in North America.
Enjoy the experience...
The next performance won’t be until 2024!

Sources:
Mass Audubon, Living with Wildlife, Cicadas, <http://www.massaudubon.org/Nature_Connection/wildlife/index.php?subject=Insects&id=4>
The University of Michigan Museum of Zoology, Insect Division, Periodical Cicada Page, <http://insects.ummz.lsa.umich.edu/fauna/michigan_cicadas/Periodical/Index.html>