Cicadas are large plant feeding insects known for their loud, shrill noise and discarded shells (called exoskeletons) that cling to trees and other vegetation. Cicadas belong to the suborder Auchenorrhyncha along with other hemipterans, such as leafhoppers and spittlebugs. These insects are found worldwide, though their presence in the United States is restricted to the southern and eastern parts of the country.
Cicadas are big, thick-bodied insects, measuring about 1 to 2 inches long. Their large compound eyes come in shades of black and red, though they sometimes emerge with white or blue eyes. Cicadas also have three simple eyes (called ocelli) in the middle of their head. The cicada’s wings are large and have thick, prominent veins. Despite their size, cicadas have relatively small antennae.
Annual, or dog-day, cicadas are often green or camouflaged in color. These cicadas spend up to five years feeding as nymphs underground, but populations emerge every year. Periodical cicadas have a black body and either spend 13 or 17 years underground. Cicada adults die shortly after mating.
Cicadas have an incomplete metamorphosis: eggs hatch into nymphs, which then turn into adults. Cicada nymphs go through four instars, or life stages, before the adult stage. Cicada nymphs bear some resemblance to adults, but at the same time, look quite different. They are cream or tan in color and do not have wings; rather, they have six legs, the front two of which are large and used for digging their way through the soil. Young nymphs appear almost translucent and look a little bit like termites. As they mature, they begin to look more like their adult form but more subdued in color, keeping the nymphal cream hue.
The cicada life cycle starts with the well-known characteristic mating call. Males call females using a special body part known as a tymbal. By moving tiny muscles in the abdomen, the tymbal, which is made of a thin membrane, vibrates and creates a shrill-sounding noise to attract females.
After mating, females insert their eggs into small twigs on a tree. Eggs hatch after six to ten weeks and fall to the ground. Nymphs burrow into the ground and make an underground network in which they feed on fluids in tree roots. When ready, cicada nymphs crawl out of the ground and grab onto a tree or other nearby plant. The back of their exoskeleton splits open, and the winged adult emerges. Annual cicadas appear every year, though some cohorts may spend several years underground. Periodical cicadas only appear every 13 or 17 years. In South Carolina, the next cohort of periodic cicadas is expected to emerge in 2024. This cohort, known as Brood XIX, is a 13-year group and will emerge in several Upstate counties.
Cicadas use deciduous trees, such as hickory, oak, and pear, and shrubs as hosts. When choosing a specific host for egg-laying (oviposition), both light and the architecture of a host plant’s branches influence their selection. Plants with longer and broader branches seem to be favored by cicadas looking for a place to lay their eggs. It is unknown if nymphs prefer any host preference for feeding.
Cicadas, especially periodical species, serve as an important resource addition to the ecosystems in which they live. The mass emergence of cicadas provides a food source for many other animals in the ecosystem, and their dead bodies serve as a significant nutrient addition to plants.
Feeding by cicada nymphs is not known to cause any significant damage to the host plant. Adult oviposition results in branch flagging, where the end of the branch dies and breaks off. This type of damage generally will not harm the tree, though, during the mass emergence of periodical cicada, damage can be severe, and young trees and shrubs may be seriously impacted.
Periodical cicadas can be affected by a Massospora fungus. This fungus is parasitic on the insect and can infect the cicada in two ways. If it infects the nymph as it burrows through the soil prior to emergence, the fungus resides in the abdomen of the cicada and causes it to act strangely, generally remaining on the ground, spreading fungal spores as it drags its abdomen. Male cicadas that are infected will answer other males’ mating calls posing as females, further spreading the infection. Towards the end of the cicada’s life, its abdomen will start to fall off, revealing more signs of the infection as it displays a white mass of the fungus. The fungus renders the insect infertile. The fungus is harmless to people.
Cicadas are usually harmless to plants, regardless of whether the species is annual or periodical. However, younger and more vulnerable plants may be more prone to dying and heavy damage due to oviposition. If the need arises or if you feel as though your plant is in danger, simply netting your plant during the emergence season will keep them protected. This is generally only done if there will be an emergence of periodical cicadas, as their emergence can be predicted. It is impossible to predict the emergence of annual cicadas.