موقع د. محمود صبيح

Anyone who has ever walked out onto a dewy meadow early in the morning to come upon thousands and thousands of empty brown pods clinging to every tree trunk, every branch, and every blade of grass–and listened in awe to the almost deafening surround-sound of chirping cicadas–is unlikely to ever forget it.

It is like stepping into an alien world.

Residents of the East coast will get a chance to experience the eerie reappearance of the red-eyed 17-year cicada within days for the southern regions and weeks for the northern ones.

Their sheer numbers will be staggering, with scientists estimating this year’s invasion at thirty billion.

Some researchers think the number may be closer to one trillion.

For the past 17 years, colossal numbers of the genus Magicicada have been lying low underground, eating off tree roots and waiting for just the right day when the ground temperature reaches exactly 64 degrees, setting off their biological signal to emerge en masse from their papery shells.

The cicadas will spend several weeks in the trees mating like crazy, then die, leaving their offspring to burrow into the ground where they will wait another 17 years–or until 2030–to reappear and start the cycle all over again.

The U.S. is residence to 15 broods of Magicicada that emerge every 13 or 17 years, so almost every year there is someplace in the country that is invaded by these locust cousins. This year’s takeover by Brood II is definitely one of the bigger ones.

Even if the numbers only match the conservative estimate of 30 billion, that’s enough so that if you lined them up in a single row end to end, they would reach to the moon and back.

During the time spend underground, cicadas do not actually sleep, but feed on a low-protein fluid found in tree roots and go through four distinct growth stages, molting four times before they surface.

Males come out first, as wingless nymphs, then molt a final time to become adults.

Perched on tree branches and singing in a chorus, they await the approach of female cicadas and the rare chance to pass on their genes.

Emerging all at once in massive numbers is part of the cicada’s survival strategy.

Predators, like lizards and birds, cannot devour them all, ensuring that some will have the chance to reproduce.

Scientists are not entirely sure why the cicada’s life cycle occurs just once in 13 or 17 years, though some believe that it deters predators.

Another theory is that the odd-numbered cycles prevent different broods from competing with each other.

How these bugs know precisely when to surface from underground remains somewhat a mystery.

While cicada invasions can be mind-bogglingly massive, literally carpeting an area in every direction, they pose no danger to humans, animals or agricultural crops.

They neither bite nor sting. And while some past inundations have seen up to 1.5 million insects per acre, most urban areas experience relatively few. –Science Recorder

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