Always Something to Learn
Have you ever stopped to be amazed by the periodical cicada when they make their Springtime appearance? They are so prehistoric looking too. They intrigue me.
A behavioral ecologist with Cornell University, Walter Koenig, lead author of a paper on the Periodical Cicada, found a very interesting discovery about the insect, something so remarkable that the scientists had a hard time believing the findings. It makes one admire the complexity of nature every time science makes a hypothesis or discovery.
Many are aware that the cicada has the longest lifespan of any known insect and how they live underground for long periods of time. It has been a strange mystery how millions of them signal each other simultaneously every 13 to 17 years to undergo transformation to shed their skin and appear in mass. Partially soil temperatures, but is it something else too? After they shed, they become the winged insect we know, filling the air with the droning noise of their multitudes in flight. They are almost a horror story in the making.
They are a bane of farmers and growers everywhere as they engulf trees and lay damage in their path. The eggs are laid in the trees and by mid-summer, then they drop to the ground for their long underground stay. The cycle of 13 to 17 years begins once again.
There are two basic types of Cicadas:
Periodic, 2-8 year cycle – These insects are seen each year, although from a different brood each year. Their life cycle is staggered. Because a different brood is hatching each year it seems like they are an annual hatching. They should be wriggling out of the ground many places about now when soil temperatures are 64°.
13 to 17 year cycle – This group does not appear every year. When they do emerge, it is in huge numbers. They are the ones in the study. The last major swarm, Brood X, surfaced in 2004, but Brood II is scheduled for the East coast this year. (source)
Cicada are seen in many areas of the country in small numbers each year. When a cicada brood hatches, it is a completely different occurrence. They emerge by the thousands, or even by the millions.
What Science Thinks is Happening
Suggested by scientists, the Cicada is timing the event to coincide with a drop in bird populations. Birds are their main predator. This hypothesis was developed with 45 years of avian population data compiled by the North American Breeding Bird Survey. The group noted the rise and fall of 15 species of birds that target the Periodical Cicada in the study.
This disparity of predator/prey is not what occurs in nature on a normal basis, in fact, it is quite the opposite generally. Predator and prey usually correspond in proportional numbers. It was noted that birds will decimate a cicada population that emerges out of sequence.
“So how do the cicadas manage to manipulate the birds over these long cycles?” was a question asked by the study. It certainly helps to explain the long time spent underground if they are correct. It has been long thought that avian predation was a factor in periodical insects, but they still do not know how the cicada regulates bird populations to low levels.
The 15 bird species were selected because they were birds known to dine on the Cicada. The analysis showed a decrease in the number of these birds when the Cicada emerged. After the cicadas emerged, the birds increased. It seemed more than a coincidence, to where the cicada is manipulating the population in some way, at least in that more birds were hatched after they became abundant.
Another study Koenig did reveals there is an enormous effect of biomass that cicadas have on the environment. They improve environmental conditions by enriching nutrients for soil after their death. For such a destructive insect, it has a lot science does not know about it, and some it does which shows it as an important part of the ecology of an area.
This image above of the very alive, but mortally wounded cicada, is from the post Plants Can Call 911 – So Says Science. It really was an interesting study.
This article, from Science Now is a bit more readable than the scientific paper in the link above if you want to know more on this fascinating study. (source)
Did you know adult Cicadas don’t eat? “Rather, damage to trees is caused by the adult female as she cuts slices into twigs to lay her eggs. Shortly after mating, the male Cicada dies.” (source) This site also lists the states where the 2013 brood will affect. They list plants and trees that are most damaged as well.
How about frying them up? Here is a reporter that did just that and he said they don’t taste like chicken! (source)