Go out into the woods in the central swath of Pennsylvania during the next month and revel in the noisy sex foreplay of the cicada.

The big, red-eyed, black and orange bugs, up to 2 inches long, have been living underground for 17 years and when tens of millions of them emerge -- likely beginning this weekend as temperatures heat up -- the males among them waste little time and no subtlety in loudly announcing they are in the mood.

Very soon, the wooded hills from Georgia through Pennsylvania and west through Kentucky will be alive with the sounds of mating music.

"I have yet to hear any singing in Pennsylvania," said Greg Hoover, an entomologist at Penn State University. "But it wouldn't surprise me at all that with the warmer weather we will begin to hear them this weekend."

Different "broods" of the periodic 17-year locust emerge each year in different areas along the Appalachian Mountains, through the mid-Atlantic states and into New England. This year's emergence, Brood XIV, is one of the largest and most widespread, stretching through parts of 13 states. Mr. Hoover said three different species of cicada make up Brood XIV, each with a different mating call that they produce by rapidly vibrating ribbed membranes on their backs and amplifying the sound through their hollow abdomens, which act like echo chambers.

The most common species makes a high-pitched noise that sounds like "pharaoh" but with an extended "ro" at the end; another makes a series of ticks and buzzes; and the third sounds like one of those golf course sprinklers that shoots out streams of water along a graduated arc -- thwit, thwit, thwit, thwit -- and then resets.

The noise made by one male cicada can be heard a quarter mile away, and when they band together for daytime serenades, the cicada "roar" or "scream" can be deafening. In response to this full-volume courting from the men's glee club, the female cicada, much less demonstrative, gives a subtle flick of her veined, cellophane-like wings, indicating she is receptive.

They're already out and singing around Ashville, N.C., Knoxville, Tenn., and through southeastern Kentucky, but cold, wet weather has delayed their emergence in the northeast, said Roy Troutman, a naturalist and nature photographer living near Cincinnati -- what will be the western edge of the this year's brood.

"They're about two weeks late around here, but once we get into the 80s this weekend we're going to see a lot of activity," said Mr. Troutman, who traveled north of Chicago last year to see and photograph Brood XII.

In Pennsylvania, historical records for this year's brood indicate they will be heard and seen in 24 of the state's 67 counties, but not in Allegheny County or the southwestern part of the state.

"Things should really be hopping in the curve of the Appalachian Mountains from Bedford up through State College and into Wyoming County," said John Rawlins, associate curator of invertebrate zoology for the Carnegie Museum of Natural History. "We haven't heard anything much about them in Pittsburgh because they won't be coming out here. We'll have to travel to see this bug."

The last cicadas to appear in southwestern Pennsylvania were in Brood VIII in 2002, and before that there was Brood V in 1999, which will also be the next to appear locally in 2016.

Cicada fans should make it a point to enjoy the noisy woods this year because broods XV, XVI and XVII are extinct. No one knows why. The next periodical cicada emergence in the mid-Atlantic area will not occur until 2012.

Often and mistakenly referred to as "17-year locusts," cicadas are not related to the large migratory grasshoppers that famously plagued Old Testament Egyptians.

"We hear them referred to as locusts," Mr. Hoover said, "and that may have started with the American colonists, who, being Biblically informed, put that tag on these insects. But actually they're a unique species to northeast North America."

Over the next six to eight weeks, the cicada nymphs will crawl up out of the two-foot deep holes in the ground that they burrowed into in 1991, when Boris Yeltsin was elected president of Russia and parades were held to welcome back troops from Operation Desert Storm, and where they have spent the last 17 years sucking sap from tree roots.

When they emerge they will climb up whatever is handy -- nearby trees, telephone poles or houses -- and pop out of their last nymphal skins to emerge as adults and take wing, leaving behind hollow brown exoskeletons that look like crunchy alien popcorn hulls.

The adult cidacas, which do not sting, bite or harm people or animals in any way, have no defense mechanisms to ward off predators, save their periodic emergence, the result of some evolutionary control mechanism, and their sheer numbers.

They live for about three weeks, during which their primary purpose is to mate. Females lay their eggs in trees. When the eggs hatch, ant-sized white nymphs fall to the ground and burrow into the soil for the next 17 years.