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Cicada, the Summer Screamer

As you walk beneath the Mopani trees in camp in the early summer (November – December), you will experience the air piercing shrills that make your ears and head buzz.

If you’ve ever wondered what the mysteriously hidden creature is that makes this sound, you have found your answer here. The vocalist is the cicada, the bug that screams.

What are they?

  • The cicada looks like a strange mix of cricket, fly and moth, with some thinking it is a beetle, but the truth is that it is none of these. The cicada is in fact a bug, belonging to the Hemiptera family (true bugs) which are insects. In particular, it belongs to the suborder, Auchenorrhyncha, which means they are in the same group as aphids, leafhoppers and spittlebugs.
  • There are about 1300 cicada species worldwide, 150 occur in South Africa. 
  • Cicadas are NOT “Christmas Beetles”!
  • There are two groups that fall under the super family Cicadoidea (cicadas). These are Cicadidae and Tettigarctidae. The tymbal organs (the organs that produce the cicada’s loud sound) in the Tettigarctidae are not as well developed as in the Cicadidae.

Where do Cicadas live?

  • Cicadas are found on every continent in the world, except for Antarctica, as they prefer warmer climates. Many species occur within specific biogeographical regions, giving this insect a high degree of local endemism. Cicadas spend most of their lives developing as nymphs in the soil before they emerge as adults. They then live in trees where they feed on plant sap with their mouth parts (proboscis) adapted for sucking.

Life cycle:

  • The cicada is known for its synchronised life cycle, with some species taking two to seventeen years as nymphs before reaching adulthood. This potentially classifies the cicada as the insect with the longest larval development stage in the world. 
  • The breeding cycle begins when adults mate after the males lure the females with their attractive cicada songs.
  • After mating the female lands in a tree, and uses her saw-like, egg laying organ (ovipositor) to fashion a slit into the bark. This is where she lays her eggs, some females lay up to 400 eggs at a time. These eggs hatch and the nymphs drop to the ground where they burrow down to depths of 2.5 meters deep into the soil. Cicada nymphs excavate chambers close to plant roots where they feed on sap. The nymphs continue to develop until they reach the final stage known as instar, when they tunnel to the surface and exit the soil.
    Emergent cicadas land on plants where they shed their skins for the final time, morphing into adulthood.
  • The males die after mating and the females die after laying their eggs.

The Cicada song:

  • Unlike similar insects, such as crickets, the male cicada does not use stridulation or the rubbing together of body parts to make their loud sound. Instead, they have a unique noise making organ, called a tymbal, located on the front side of the hollow body of the male that acts as a sound box.
  • The noise is made with the contraction of muscles acting against the tymbals, which produces clicks which are combined into continuous notes. The cicada actually has the ability to manipulate the sound by changing its position in relation to a surface.
  • Each species has its own distinctive mating songs and acoustic signals that ensure only appropriate mates are attracted to the sound. The sound and singing strategy of males differs between species, and often it is more than one male species singing at one time. Cicada experts are able to distinguish between the different songs of the males, with one species imitating the sound of a sizzling skillet, another sounding like a high pitched lawn mower and a third with a song that sounds like its repeating the word “pharaoh” in a droning tone.
  • Some male species prefer to sing alone, while others, like the ones on Ingwelala, prefer to sing in chorus, congregated in one particular location. But whether these little guys sing alone or together, to sit beneath them on a bench will surely leave you with a buzzing head!
  • Some cicada species produce sounds that measure up to 120 decibels, which is among the loudest of all insect-produced sounds. The song is loud enough to cause permanent hearing damage in humans should the cicada sing too close to the ear. In contrast, some of the smaller cicada species have such high pitched songs, they are inaudible to humans. So it pays to keep your distance!
  • In addition to the mating song, many species have a distinct distress call, usually a broken and erratic sound emitted when the insect is seized or panicked. Males also produce “encounter calls”, whether in courtship or to maintain personal space within choruses.
  • Only the males sing, which attracts the females, which are lured by the sound to his position. A female responds to a male with a flick of her wings. The two gradually draw close to one another until they meet for mating.

Cicada Anti-Predator Tactics:

  • These insects have excellent camouflage. You may have noticed the cicadas on your windows look like bark, with disruptive patterns on their body that allow them to blend in with the trees. Have you ever been able to look into a tree and successfully spot an African cicada singing? Try it when next you visit the Reserve.
  • Cicadas possess wings that do not reflect light, therefore preventing the typical insect cuticle shine.
  • Cicadas are very strong fliers, who are able to fly at high speeds escaping their predators.
  • Scientists say that the reason behind the cicada’s long period of nymph stage is to “outsmart” their predators by having a life cycle that is out of sync with specialized cicada killers, such as the cicada killer wasp and the praying mantis.

Diet:

  • Cicada nymphs suck sap from the xylem of various species of trees. While it is common folklore that adults do not eat, this is not true because adults do drink plant sap utilizing their sucking mouthparts.

The Cicada’s value to animals:

  • The explosion of cicadas in the summer time is like nature’s Christmas treat to the multitudes of different life forms that occur in the bush veld and other ecosystems in South Africa. They provide an important energy source for birds, reptiles, mammals, other insects and even fungi. The cicada’s presence means that smaller animal viewing around your bungalow will likely boom. Just this morning I woke up to observe a dozen birds on the patio feasting on the cicada bodies failing to return to their roost from the night before.
  • Therefore, the great abundance of cicadas in the summer is probably a major contributor to the breeding and survival success of other species, which have an important ecological role to fulfil. Cicadas help to keep the natural ecosystem functioning.

The Cicada’s Value to Trees:

  • Since cicadas parasitize on trees, they contribute to biodiversity by preventing their host tree populations from out competing other tree species.
  • Cicadas provide trees a service by pruning the weak branches of a tree, the tree benefits by not having to waste energy supporting a weak or diseased branch.
  • Cicadas provide natural fertilizer for trees through their decaying mass, recycling much needed nutrients into the soils.

The Cicada’s Value to People:

  • Cicadas are an important food source to humans as well as animals. In some places, these insects are people’s staple diet.

Other interesting Cicada facts:

  • In China male cicadas are kept in cages in people's homes so that the homeowners can enjoy the cicadas' songs.
  • Cicadas give away their pending emergence by building thousands of "chimneys" or "stovepipes" on the ground, especially near trees. They will emerge through these structures when they leave the ground and crawl up trees and shrubs.
  • The transparent wings of cicadas are said to filter out ultraviolet light. People who have placed a cicada wing on their skin prior to exposure to the sun have noticed that they do not tan under the wing.
  • Cicadas are said to make good eating because they are low in fat and high in protein. They are considered a delicacy by many people around the world.

 

by Paige Ezzey
Conservation Intern