Cicadas

PERIODICAL CICADAS EMERGING IN ILLINOIS

     CHAMPAIGN, ILL. -- Periodical cicadas with a 17-year life cycle are emerging, right on
schedule, in sections of central Illinois this month, according to an entomologist at the Illinois Natural
History Survey.

     Cicadas, flying insects related to aphids and leafhoppers, have multiple year life cycles.  Most
are non-periodical cicadas, often called "dog day" cicadas, found annually in the summer and early
fall, well known in Illinois for their loud, buzzing cicada "songs" produced by males in large choruses.
   
     Of more interest to entomologists, horticulturists, nursery and orchard owners are broods of
periodical cicadas, emerging once every 13 or 17 years, ready to cover and feed on trees and shrubs,
according to INHS entomologist Dr. Christopher Dietrich.

     "Brood III of 17-year cicadas, which last emerged in 1980, is back in a large section of Iowa,
parts of northern Missouri and portions of central Illinois," said Dietrich.  "Periodical cicada nymphs
emerge and head for tree and shrub branches.  Mature plants usually survive without much damage.
We advise nurserymen not to plant new trees the year before an emergence because of the potential
for damage to young plants when tens of thousands of cicadas latch onto peripheral twigs."

     Entomologists aren't sure what prompts periodical cicadas to emerge after years of
underground feeding and growth.  In the spring of their 17th year, weeks before they emerge, cicadas
build tunnels from their burrows.  Members of the brood can be expected to emerge almost
simultaneously. 

     Cicadas do not bite or sting, nor are they known to transmit
disease.  Males and females generally fly away when approached and may elicit a loud buzzing sound
if handled as they try to fly away.
         
     Male periodical cicada "songs" are produced by vibration of the membranes at the base of the
insect's abdomen, producing a distinctive resonance.

     The male cicadas' calls attract females to mate.  Eggs inserted into living twigs hatch by mid-summer, sending nymphs crawling off the plant underground to repeat the periodical cicada life cycle.

     The 17-year periodical cicadas emerging in Illinois this summer are expected to be
concentrated in Brown, Fulton, Henderson, Knox, McDonough, Schuyler and Warren counties in the
west-central part of the state.  There may also be some occurrences in Champaign, DeWitt and Piatt
counties in east-central Illinois.

     "There are twelve different broods of 17-year cicadas, each of which emerges during a
different year and occupies a different geographical area," said Dietrich.  "Each brood consists of as
many as three different cicada species that are distinguishable based on their different courtship calls."

     Other broods of 17-year periodical cicadas are expected to emerge in extreme eastern Illinois
in 2004 and in northern Illinois in 2007.  A brood of 13-year periodical cicadas is expected to emerge
in central and southern Illinois in 1998.

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