Periodical cicada, shell

A periodical cicada crawls from the ground as a nymph that leaves a shell when a winged adult emerges from it.

It is a good thing that Brood X of periodical cicadas is not subject to pandemic restrictions against larger gatherings: They would be extreme offenders.

These red-eyed insects are not affected by COVID-19 and, unlike people, not scolded nor prosecuted for chumming together in numbers greater than 50. That is fortunate because this month they will begin creeping out of the earth by the millions and billions, mingling en masse to create quite a natural phenomenon.

Periodical cicadas are bugs that spend most of their lives, years, in the ground as nymphs feeding on the sap of tree roots, then emerge in their last few weeks to transform into winged adults to reproduce. Females then lay eggs to renew the life cycle, after which all the adults die within a few weeks.

The periodical cicadas are arranged by nature into broods, each brood emerging and reproducing within a short period in the same years. There are 15 recognized broods in the United States, 12 of which mature over 17 years and three of which mature and emerge every 13 years.

This year is the climax of the life cycle of Brood X (that is Brood 10, expressed in Roman numerals), which also is called the Great Eastern Brood. Brood X earns that title because of its great geographic spread, covering all or parts of 15 states, including Kentucky, Tennessee and Illinois hereabouts.

The periodical cicada as an adult is about 1.5 inch long. It has a double pair of wings that are translucent — clearish but tinted in orange. The body is black and the legs and veins in the wings are more vivid orange. The most striking feature are the insect’s bright red eyes.

The fiery red eyes make the periodical cicada look a bit devilish, but it is totally harmless. This bug cannot sting, and it doesn’t bite or otherwise harm us.

There are similarities but clear differences between the periodical cicadas and the annual cicadas. The larger annual cicadas (2-2.5 inches) are greenish black of body and legs. They have wings that are mostly clear with hints of green and black in the veins.

Unlike the periodicals, the annual bugs appear every year, mostly June-September, in much smaller numbers. Where there might be dozens of annual cicadas in a small area, the mass-hatching periodical cicadas more likely will be there by the thousands.

Our Brood X bugs, 17-year cicadas, should start popping out late this month. That is triggered by soil temperatures reaching 64 degrees Fahrenheit. Once it starts, the emergence should last about three weeks. Some should be around until about the end of May.

Cicadas will pop out of the earth, each leaving a hole the size of a pencil, mostly around the trees the roots of which have sustained them for the past 17 years. Each wingless nymph will find a vertical surface, climb up a little and there the nymphal shell will split and a winged adult cicada will emerge from inside.

Where emergence is plentiful, dried remnant shells of nymphs accumulate to show how many adults have passed through that stage.

Male cicadas dry their wings, then fly to the upper branches of nearby trees. There, each vibrates a membrane in its abdomen, which creates an improbably loud whirring sound th at the male uses to call females to mate.

After boy/girl bug pairs mate, the females soon use mouthparts to cut slits in the smallest of tree branches. Into these they lay tiny eggs. Later, the eggs hatch out new cicadas, smaller than rice grains, that drop to the ground and dig in where they will mature over the next 17 years.

Amid heavy periodical cicada hatches, even casual observation should reveal scads of leftover nymphal shells and plenty of the winged, red-eyed adults. Even more adults will be out of sight up in the trees.

What is most evident, however, is the mating song of the males quivering their belly membranes. Each bug’s call can be impressively loud, and when a few thousand calling cicadas nearby cut down on it, the total sound can be an oppressive din. The accumulated drone has been described as being louder than a jet airplane.

It is not known to be harmful, but a vast number of wiggling cicada abdomens tuning up at the same time can hardly be ignored and people have complained of being agitated, unnerved or somewhat maddened by the constant overwhelming buzz.

When Brood X breaks loose in our region, they should not be just everywhere. But especially in areas of prevalent timber, the bugs most likely should at least appear in impressive swarms in prime locations.

It will be messy and annoying for some people, but nothing like a “plague of locusts” to which periodical cicadas historically were compared. On the other hand, many species of wildlife will relish the emerging insects as a special food source. Cicadas apparently are about as nutritional as they are defenseless and, in season, plentiful.

If you are inclined to try them as a gastronomic bonus, however, be sparing about it. Veterinarians say it is common for pets to eat them, but excessive consumption can lead to gut problems because high numbers of the exoskeletons of cicadas can lead to extreme indigestion.

Maybe just enjoy the nature novelty and leave eating the cicadas to other critters.

Steve Vantreese, a freelance outdoors writer, can be contacted at outdoors@paducahsun.com.

Steve Vantreese, a freelance outdoors writer, can be contacted at outdoors@paducahsun.com.