In the dog days of summer, when you start sweating before you even step out the door, your ears are assailed by loud noises coming from the trees above. Looking for monarch caterpillars you may instead find multitudes of these empty brown shells of the annual cicadas, which have grown to adulthood so they they sing all day to attract a mate. When young cicada nymphs hatch from their eggs, they dig themselves into the ground to suck the liquids of plant roots. They spend several early life stages in these underground burrows before surfacing as adults. The process varies in length but often takes a number of years. Cicadas are also famous for their penchant for disappearing entirely for many years, only to reappear in force at a regular interval. There are some 3,000 cicada species, but only some share this behavior (the 17-year cicada is an example). Others are called annuals because, although individuals have multi-year lifecycles, some adults appear every year. The dog day cicada, for example, emerges each year in mid-summer.Periodical cicadas emerge in specific locations once every 17 years in the northern part of their range, and once every 13 years in the southern part. Different groups called “broods” emerge somewhere in the eastern United States almost every spring. Massive brood emergence is believed to overwhelm predators, which are mostly birds. This ensures that enough survivors will be left behind to reproduce.Periodical cicadas have black bodies, red eyes, and red-orange wing veins in two pairs of clear wings that are held roof-like over the abdomen. These clumsy fliers often stay in the upper canopy of trees while they are active from late April thru June. Encounters with periodical cicadas can be unnerving to some but these insects cannot sting and do not harm humans, livestock, and pets. Periodical cicadas do not create destructive plagues, as some locusts (which are actually grasshoppers) do, though tens or hundreds of thousands of insects may crowd into a single acre. Large swarms can overwhelm and damage young trees by feeding and laying eggs, but older trees usually escape without serious damage.