Cicadas

Periodical cicadas (Magicicada septendecium) 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 "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. 

The "dog-day" or annual cicadas (Tibicen spp.) appear during the long summer days of July and August. These cicadas have two-to five-year life cycles but their broods overlap and some appear every summer.

Male cicadas are capable of making a loud buzzing noise and squawk when disturbed. The males often synchronize their buzzing in trees which produces a deafening noise. It is believed that such droning and squawking is effective in deterring predators. Cicadas do not bite or sting and have no known toxic chemicals. Adult cicadas are usually a nuisance due to their sheer numbers and loud, piercing call.

Description and Life Cycle

Periodical Cicadas: Adult periodical cicadas are sucking insects, about 1½ inch long. They appear from May through July and are most numerous in the last two weeks of May and first week of June. They are black and have reddish-orange eyes and legs. Adults have clear wings with orange veins that are held roof-like over their bodies.

Immature periodical cicadas (nymphs) develop underground and suck juices from plant roots. After 13 or 17 years below ground, mature nymphs emerge from the soil at night and climb onto nearby vegetation or any vertical surface. They then molt into winged adults. Their shed outer skins (exoskeletons) are found attached to tree trunks and twigs. The emergence is often tightly synchronized, with most nymphs appearing within a few nights. Adult cicadas live for only two to four weeks. During this short time, they feed  relatively little. Male cicadas sing; male courtship songs attract females for mating; females are silent.

After mating, females lay their eggs in twigs. Cicada eggs remain in the twigs for 6 to 10 weeks before hatching. The newly-hatched, Periodical Cicadas ant-like nymphs fall to the ground where they burrow underground to feed. During the spring of the emergence year, periodical cicada nymphs may build mud tubes that project 3 to 5 inches above the soil, apparently to escape wet or saturated soils. These tubes are often mistaken for the tubes that crayfish build.

Annual Cicadas: Annual cicadas are larger than periodical cicadas and have green to brown bodies with black markings and a whitish bloom. Their wings have green veins. Annual cicadas usually emerge from June through August. Their emergence is scattered over this time and they rarely emerge in noticeable numbers. Annual cicada males also sing to attract females. The cicada killer wasp often captures these insects to provision its nest in the ground.

Damage 

Periodical cicadas damage trees above and below ground. The most obvious damage is that caused by egg laying in small twigs, causing twigs to split, wither, and die. The symptom is called “flagging" and it is especially serious on young plants (four years or ounger) because more of the branches are of the preferred size. Some of the more favored trees for egg laying include maple, oak, hickory, beech, ash, dogwood, hawthorn, magnolia, willow, apple, peach, cherry, and pear. Flowers, vines and shrubs include: Rose of Sharon, rose, raspberry, grape, blackeyed Susan, hollies, spirea, rhododendron, viburnum, juniper, and arborvitae. More than 270 species of plants have been noted as hosts for egg laying female cicadas. Damage is also done by the nymphs, which suck sap from roots. Prolonged feeding by nymphs on a tree's root system may reduce plant growth and fruit production.

Since there are no serious problems with periodical cicadas in Rhode Island, and since annual cicadas seldom, if ever, cause damage, cicada control is unwarranted in this state.

Adapted fromthe Ohio State University Extension, 1999