Recently in the Nature Department:
June 1, 2007
Invasion!
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| Larger ImageCicada on a Car Tire |
They're baaaaaaaaack!
Meet one of the Chicago area's least favorite forms of animal life, the cicada, Magicicada septendecim, also known as the 17-year locust. John Ruberry reports he's just beginning to see signs of them around his neighborhood, which is a few miles from where I live. However, when I went to visit my parents in the southwest suburbs, they were all over the place.
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| Larger ImageCicada on a Branch |
Actually, although they look a bit like locusts, insects of the cicada family are classified as part of the order Hemiptera, whereas locusts are classified under the order Orthoptera. The cicadas we're all talking about are the periodic cicadas of the Magicicada genus, which have evolved an interesting strategy to deal with predators.
For most of their lifecycle, they hide underground, where few predators can find them. The problem with this strategy is that other cicadas can't find them either, which makes mating kind of difficult. However, if they emerge to mate, they get eaten by predators.
Many insects simply live with that risk as part of the cost of reproduction, but Magicicada has found a more interesting strategy: They hide underground for a very long time—17 years in this case—and then emerge all at once.
This overwhelms the predators, which can only eat a small fraction of the suddenly enormous cicada population. The rest of the cicadas survive to mate and reproduce.
The periodic cicadas come in several species. Based on their 17-year period and the markings I can see (especially the orange spot between the eye and wing on each side), I believe these are all Magicicada septendecim, but I am far from an expert.
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| Larger ImageUnderside of a Cicada |
Although we're just starting to see a few of these now, the Chicago area will soon be deluged with hundreds of millions of them. My wife still shudders at the memory of the previous emergence in 1990 when we attended a friend's wedding and she had to walk from the car to the outdoor reception on a thick carpet of dead cicadas.
Despite their large size and colorful appearance, cicadas are actually quite harmless. They don't bite, and they don't carry any diseases. They're not even a threat to crops. They just like to come out every 17 years for a big party.
So if you should happen across one of these fellows in the next few weeks, be sure to say "hi"...
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| Larger ImageHi There! |
...and then stomp on them because, really, we've got enough of them already.
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