Why cicadas?

The Question

[e-mail; 18 Feb 1997]

Dr. Boyer:

I would like to know if you can tell me 5 things good about cicada, because all the information I found said was noise and how to kill it.

But I had a expositon and until now I can't found anything good .

Thanks, Adriana

[Adriana Torres, Universidad de Monterrey, México]

Some Answers

Dear Adriana:

Thank you so much for your note inquiring for five good things about cicadas. I think that I can more than fulfill that quota. First, there are very relatively few organisms on the Earth which have important material benefits for humans, if one takes into consideration the total estimated number of species, which may be in the millions. Biologists have pointed out that the total diversity of life probably is important in maintaining balanced ecosystems: therefore, no single species which is not harmful can be disparaged simply because it has no direct economic benefit.

Now to cicadas! Their main benefits are intellectual and aesthetic. Here is my list:

I. Practical benefits

A. Food for birds and small mammals

B. Human food (as a delicacy; see the link to skewered cicadas, a Chinese recipe)

II. Intellectual benefits: scientific interest

A. Cicadas are the only insects which can make sound by all three methods present among insects.

B. Our 17-year cicadas here in North America are believed to be the longest lived insects in the world. How do they manage to live so long, when other insects generally have short lives?

C. The songs of the various cicada species are the most complex of any insect. Some in the tropics sound deceptively like birdsong! The study of bioacoustics must include cicadas.

D. The periodical cicadas manage to appear right on schedule at 13- or 17-year intervals. How do they do this? This is a remarkable example of a biological clock, or a biological calendar!

E. The broods of periodical cicadas do not readily interbreed, and yet are very similar. They provide an instructive example of speciation, and also an evolutionary puzzle of great interest.

III. Aesthetic value

A. Cicadas are very attractive, if one studies them in detail and can overcome the initial (and very natural) human aversion to crawly things. The subtle colors and intricate wing-venation are especially impressive. A cicada emerging from its nymph-shell undergoes wonderful color changes as its new integument hardens. I have photographed this, and have won awards with some on my pictures.

B. Cicadas in some cultures are a symbol of longevity (China, ancient Greece). This is because they emerge from the earth and become "reborn" by shedding their drab, earthy nymph-skin, and then ascend to toward the heavens where they live on very little earthly nourishment. (The ancient Greeks even believed that cicadas lived on dew alone, which is not at all accurate!)

C. The song of the cicada is a part of the summer experience in many countries, and is enough to evoke memories and emotions of past years: it is one of those things in which ties together our years in a way which provides continuity, and the reassurance that the world (with life in it) continues.

I am disturbed to find that many publications on cicadas are mainly concerned with their "control," that is, how to eliminate them. The very rare damage caused by cicadas is generally so minor, that it is better simply to leave them alone. I would like everyone to become more alert to the exciting beauty and interest of nature: such an attitude of appreciation makes us all better people.

Regards,

Paul S. Boyer, Ph.D. 

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