 | Annual Cicada - Tibicen spp.
Also commonly known as dog day cicada
Order Homoptera / Suborder Auchenorrhyncha -- hoppers / Infraorder Cicadomorpha / Superfamily Cicadoidea / Family Cicadidae -- cicadas
Live adult cicadas photographed at West Chicago Prairie, DuPage County IL August 24, 2004.
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Annual Cicada - Tibicen linnei
| | Cicadas are flying, plant-sucking insects of the Order Hemiptera; their closest relatives are leafhoppers, treehoppers, and fulgoroids. Adult cicadas tend to be large (most are 25-50mm), with prominent wide-set eyes, short antennae, and clear wings held roof-like over the abdomen. Cicadas are probably best known for their conspicuous acoustic signals or "songs", which the males make using special structures called tymbals, found on the abdomen.
All but a few cicada species have multiple-year life cycles, most commonly 2-8 years. In most cicada species, adults can be found every year because the population is not developmentally synchronized; these are often called "annual" cicada species. In contrast, populations of the periodic cicada species are synchronized, so that almost all of them mature into adults in the same year. The fact that periodic cicadas remain locked together in time is made even more amazing by their extremely long life-cycles of 13 or 17 years.
Periodic cicadas are found in eastern North America and belong to the genus Magicicada. There are seven species -- four with 13-year life cycles (including one new species described in 2000), and three with 17-year cycles. The three 17-year species are generally northern in distribution, while the 13-year species are generally southern and midwestern. Magicicada are so well-synchronized developmentally that they are nearly absent as adults in the 12 or 16 years between emergences. When they do emerge after their long juvenile periods, they do so in huge numbers, forming much denser aggregations than those usually achieved by cicadas. Many people know periodic cicadas by the name "17-year locusts" or "13-year locusts", but they are not true locusts, which are a type of grasshopper.
Please note our terminology: we have taken exception to the use of the word "periodical" to describe these insects. It escapes us as to how supposedly intelligent scientists have fallen into that error. The proper word is "periodic", as any cursory perusal of a dictionary would show. | 
Annual Cicada - Tibicen canicularis
There are about 2,000 species of cicadas worldwide, most of them found in
tropical or temperate regions. Most of the more than 100 species found in
North America have short life cycles, between two and eight years. They are
known as annual or dog-day cicadas because they usually emerge during mid to
late summer (July and August).
A small number of cicada species have synchronized their life cycles so that
they emerge from the ground in their billions only once in every 13 or 17
years. These are known as periodical cicadas but are also commonly called
17-year cicadas, 13-year cicadas, or locusts. They are not locusts, however.
The dog-day cicada is dark with green markings. The periodical cicada has
protruding red eyes and orange legs; adults have clear wings with orange
veins. It is not known how periodical cicadas synchronize their life cycles
over 13 or 17 years—or how they manage to count out the years. But by
emerging at such long intervals in such vast numbers, as many as 1.5 million
insects per acre, according to one estimate, they have evolved an effective
strategy to overwhelm predators by sheer volume. The mass emergence of
periodical cicadas provides an unlimited feast for birds, snakes, and
mammals. Even humans have been known to eat the harmless insects (Cicadas
are not poisonous and do not bite or sting).
Once the predators have eaten to capacity, there are still millions of
cicadas left over to produce the next generation. Predator populations
cannot build up in response to such a massive food supply, because the
cicadas appear above the ground only once in every 13 or 17 years.
Periodic cicadas are found in eastern North America and belong to the genus
Magicicada. There are seven species, four with 13-year life cycles, and
three with 17-year cycles. The three 17-year species are generally northern
in distribution, while the 13-year species are generally southern and
midwestern. Periodic cicadas generally emerge in May and June, apparently
when the soil temperature reaches 64° Fahrenheit (18° Celsius). This means
that emergences in southern and low-lying areas occur earlier in the summer
than in the cooler northern locations.
Magicicada cicadas synchronize their life cycles only in local areas. There
are 12 broods, or year classes, among the 17-year cicadas and three broods
of 13-year cicadas so that in almost any given year it is possible to find
adult periodic cicadas somewhere in the U.S. |
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