Periodical Cicadas

Description

Periodical cicadas are insects classified in the order Hemiptera, along with aphids, leafhoppers, and shield bugs. Many species of insects are mistakenly referred to as “bugs,” but only hemipterans are considered to be “true bugs.” Adult periodical cicadas are black from above and orange underneath. They have bright red eyes and clear, membranous wings with black veins. They’re just over an inch (2.5 centimeters) in length with a three-inch (seven-centimeter) wingspan.

Range

Each brood of periodical cicadas has a specific range, but all are found in the eastern and midwestern United States. Periodical cicadas are associated with deciduous trees and shrubs. They sometimes cause harm to young trees, but this can easily be prevented by covering the plants with cheesecloth until the adults die out. Cicadas are mostly beneficial. They prune mature trees, aerate the soil, and once they die, their bodies serve as an important source of nitrogen for growing trees.

When cicadas come out, they’re eaten by just about anything with an insectivorous diet. The fact that cicadas emerge in the millions, however, makes them relatively resilient to predation. Even when a ton of them are eaten, there are still plenty more ready to mate and lay eggs.

Diet

Cicadas have modified mouthparts to feed on liquids rather than solid material. Larvae suck juices from plant roots, while adults suck fluids from woody shrubs and trees.

Life History

Periodical cicadas are best known for their extraordinary, highly synchronized life cycles. They spend most of their lives—13 or 17 years, depending on the species—in larval form, burrowed beneath the soil and feeding on fluids from plant roots. In springtime, they emerge from the soil and complete their final molt into adulthood. Each individual in a brood emerges within weeks of one another.

Males cluster in groups and produce loud choruses to attract females to mate with. After mating, female cicadas excavate furrows in slender tree branches and deposit their eggs. The larvae hatch, drop to the ground, and burrow beneath the soil again. The year that each brood will emerge is easily predicted by counting forward 13 or 17 years from their last emergence.

Annual cicadas exist as well. These cicadas live about two to eight years, but because their life cycles aren’t synchronized like periodical cicadas, some of them emerge every year.

Conservation

Cicadas do relatively well in their adult stage, because they only need to survive for a short time to mate and lay eggs. There are so many of them that their numbers are minimally impacted by predation. The larval form, however, must survive 13 or 17 years in the soil, and pesticides and chemicals sprayed onto lawns can kill them. For this reason, periodical cicadas are a somewhat vulnerable group of insects.

Fun Fact

People that have sampled cicadas often say they taste similar to canned asparagus.

Sources

Animal Diversity Web, University of Michigan Museum of Zoology

Mount St. Joseph University

The Environmental Literacy Council

University of Kentucky Entomology