When the temperature is right, those nymphs will leave their holes and make their way back to the bark of the nearby tree to shed their skin, a kind of sheddable exoskeleton known as an exuvia. In their soft, whitish post-shedding form, the cicadas will wait for their new adult skin to harden and darken to their signature black. The cicadas are highly vulnerable during time (it usually takes 30 minutes to an hour), and should be avoided to make sure they survive the process.
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Under optimal conditions, there may be as many as 1.5 million cicadas on a single acre of land. How concentrated their populations depends largely on how developed the local area is. These insects can and will emerge in urban, suburban and rural places alike.