KNOXVILLE, Tenn. (WATE) — We’ve seen them and we’ve heard them: Trillions of periodical cicadas have been emerging en masse since May, according to experts at the University of Tennessee after 17 years underground.

Jerome Grant, a professor at the University of Tennessee’s Department of Entomology and Plant Pathology, spoke about the creatures as the region is already seeing — and hearing — some of Brood X emerge.

Here are 6 Things to Know About Cicadas and why the natural phenomena could be educational — and delicious.

Yes, cicadas are edible

Grant has several recipes for cooking with cicadas and other insects. He says cicadas are high in protein, low in fat, low in cholesterol and are gluten-free.

Grant says if you’re not allergic and enjoy shellfish foods, then cicadas could be tasty; some say cicadas taste like cooked asparagus or roasted almonds. If you decide to try cooking and eating cicadas, be sure they come from a safe place free of pesticides

Brood X is a 17-year periodical group

The periodical cicadas of Brood X — those that emerge every 17 or 13 years — are emerging from underground by the billions if not trillions. The last time Brood X was out of the ground was in 2004 and they will return in 2038.

It’s considered one of the largest broods ever. Brood X will be found across 15 states.

The next 13-year brood will emerge in 2024 — mainly in Middle Tennessee. Then in 2025, another 17-year brood will emerge in East Tennessee.

The life cycle of the cicada

The Brood X periodical cicadas are expected to emerge in early May, depending on the soil temperatures, and will be out until the end of June.

When they emerge from holes they dig from underground, they will climb up a vertical surface, like a tree or structure; latch on; become a hardened cicada; and emerge from their shell to sing and mate. The females lay their eggs in a slit they pierce into the tree, which turn into “nibs” that fall to the ground for the next multiyear brood. Then the mature brood dies. Their bodies serve as nutrients in the soil, or a food source for birds and animals.

The song of the cicadas

Only the male cicadas produce the mating call to females.

The sounds we hear from cicadas runs anywhere from 85-100 decibels, which is equivalent to a low-flying plane or a lawnmower.

Tennessee is home to 2 types of cicadas

Grant says Tennessee has two types of cicadas:

  • “Dog Day” cicadas emerge later in the summer each year and are large and green.
  • The periodical cicadas that emerge every 13 or 17 years are smaller and brown/orange.

Cicadas are harmless to humans, pets

Cicadas have a piercing, sucking mouthpart — it cannot chew or bite. They feed on roots of trees while underground and then feed on tree sap when they emerge.

They do not bite, or sting and are not poisonous. Some pets that overeat cicadas could get an upset stomach.