Part of Central Pennsylvania is just weeks away from the next emergence of 17-year periodical cicadas.
Millions of the insects in Brood II, also known as the East Coast Brood, have started clawing their way upward from the spots six to 12 inches underground where they've lived since 1997.
Brood II will begin to emerge when soil temperatures hit 64 degrees, which likely will occur in the latter half of May, according to Gregory Hoover, senior extension associate in Penn State's College of Agricultural Sciences.
However, evidence of their presence may already be visible in some parts of the coming emergence area, which will be focused on wooded areas such as parks, tree-lined neighborhoods and woodlands rather than open areas such as agricultural fields.
He explained, "I have noticed that in moist soil these things will produce little turrets of soil ... little clay chimneys. If you knock one of those over, inside you will find a mature cicada nymph." The little turrets, although made of soil, appear much like the mounds created by allowing very wet sand to dribble through one's fingers.
By now the nymphs have burrowed to within an inch of the soil surface and the muscle structure of their bodies is changing yet again. When that 64-degree signal comes, they will complete their exodus through inch-diameter holes, fly about clumsily, often crashing into each other and everything else around them, and then climb a foot or more up tree trunks.
From there, the males will begin doing what periodical cicadas are best known for, singing.
Each brood may include one to three species of cicada, each with its own distinctive song stylings, according to Hoover. One species produces a buzzing that sounds a lot like the word pharaoh, only drawn out over several seconds. Another clicks and buzzes.
About 10 days into the emergence, females will begin responding to the song, mate with the males and start laying their eggs in slits they cut into the twigs and branches of nearly 80 different species of deciduous trees and woody shrubs.
Hoover explained that each female will deposit 400-600 eggs. She will use "the blades of a sawlike, egg-laying device" at the end of her abdomen to puncture the bark of a twig and make a pocket in the wood. There she will deposit 24-28 eggs in two rows, then move forward to cut another pocket and lay more eggs.
The egg-laying produces the heaviest damage done by cicadas, and fruit and nut orchards in areas of particularly heavy emergence can suffer heavy pruning losses. There is some evidence that emerged adults might feed by sucking plant juices from tender young twigs, but that and the root sucking by the nymphs appear to have little consequence for most trees and shrubs.
Although the afternoon droning of the males in areas of particularly heavy emergence may seem to go on forever to people living there, adult cicadas live about three to four weeks aboveground. Most will be gone by the beginning of July, leaving behind their shed exoskeletons on tree trunks and branches everywhere.
The eggs will hatch in six to seven weeks, and then "the white, antlike nymphs work their way out of the slits and drop to the ground where they enter the soil," where they insert their piercing-sucking mouthparts into plant roots and begin drawing plant fluid. They will remain there for 17 years, metamorphosing through about five stages known as instars.
Much legend and lore has arisen around the periodical cicada since it was discovered about 300 years ago. We will explore much of that in coming days, here at PennLive.com Cicada Central.