Cicadas are a group of true bugs that constitute the superfamily Cicadoidea. They are best known for their powerful acoustic signals, produced by males using paired tymbal organs located on the first abdominal segment. These organs, along with an internal system of air sacs, produce species-specific clicking calls that primarily help attract females for mating.
Over 3,000 species of cicadas are distributed on every continent except Antarctica, with the highest diversity found in the tropics.
These insects follow a hemimetabolous pattern of development, with eggs hatching into nymphs that progressively mature into adults, bypassing a pupal stage. The nymphs spend several years underground, feeding on xylem sap, and emerge as adults only to mate, after which they die.
On average, most adult cicadas are around 1 to 2 in (2 to 5 cm) long. The largest species, the empress cicada (Megapomponia imperatoria), measures around 2.8 in (7 cm) in body length and 7 to 8 in (18 to 20 cm) in wingspan. In contrast, one of the smallest species, the small grass pygmy (Punia kolos), has a forewing length of only 0.35 to 0.47 in (9 to 12 mm).
Being insects, cicadas have a tripartite body arrangement, divided into three distinct segments: head, thorax, and abdomen.
This region bears a pair of prominent compound eyes set wide apart, as well as three small, simple eyes (ocelli) arranged in a triangle between the two compound eyes. The pair of antennae is short and bristle-like.
They are distinguished from other hemipterans by their sharp, beak-like rostrum, a structure that helps them pierce trees and suck on their xylem sap.
The thoracic region is subdivided into the prothorax, mesothorax, and metathorax, with each segment carrying a pair of legs. The mesothorax bears the forewings while the metathorax bears the hindwings. Both forewings and hindwings are large and membranous, often with visible venation in many species.
The abdominal region is segmented, with most species having nine visible segments. The first segment is highly modified in both sexes.
Males exclusively possess specialized sound-producing, drum-like organs, called tymbals, on the sides of the first abdominal segment. Each tymbal consists of a thin, dome-shaped cuticular membrane supported by a series of arched, parallel ribs. The membrane and ribs are primarily composed of resilin, a material that provides exceptional elasticity, allowing the structure to recoil easily. Beneath the tymbals are large abdominal air sacs that act as resonating chambers.
In males, the first abdominal segment is also covered by a pair of large ventral flaps called opercula. Although females lack tymbals, they do possess opercula, though much smaller in size than those of males.
The final abdominal segment of females bears the egg-laying organ, the ovipositor. Thus, in females, the abdomen appears more rounded posteriorly.
Cicadas get their name from an onomatopoeic Latin word, cicāda, meaning the sound of the word imitates the clicking sound these insects make in the wild.[1]
All species of cicadas are classified into 2 families, Tettigarctidae and Cicadidae.
Fossil records suggest that the families Cicadidae and Tettigarctidae likely diverged by (or before) the Middle Jurassic Period.[2]
The highest species richness of cicadas is in Asia, with approximately 1,000 species spread across China, India, Japan, Southeast Asia, and the Western Pacific islands. Australia has an estimated 700 species of cicadas, most of which are undescribed, and which are found in every habitat from rainforests and deserts to alpine zones and urban areas. New Zealand has over 40 species that are entirely endemic to the country.
Around 150 species are found in South Africa. While North America contains over 170 species north of Mexico, Central and South America together host at least 800 species.
Europe has over 30 species of cicadas, with the ash cicada (Cicada orni) being the most commonly found species. The only cicada native to the United Kingdom is the New Forest cicada (Cicadetta montana).[3]
Both nymphs and adults of cicadas feed on sap from the xylem of various trees, such as oak, cypress, willow, ash, and maple. While nymphs gather the sap from plant roots, adults obtain sap from stems and branches.
These insects are categorized into two major groups based on their life cycles: annual cicadas and periodical cicadas. Annual cicadas, which include members of the genus Neotibicen, Diceroprocta, Neocicada, and Okanagana, have a lifespan of 2 to 5 years, but because their generations overlap, adults appear every summer. On the other hand, periodical cicadas, which include members of the genus Magicicada found in eastern North America, have either a 13-year or 17-year life cycle, emerging in huge, synchronized broods.[4][5]
In all cicadas, the adults typically live for 4 to 6 weeks (only to mate), spending most of their lives underground as nymphs.
Male cicadas attract potential female mates with their characteristic calls. In many species, males gather in groups and create loud choruses, while in others, males wander around and use softer calls to find females. Members of the family Tettigarctidae send vibrations through the substrate instead of producing sounds. Once the pair forms, the male transfers sperm inside the female’s body.
After internal fertilization, the female uses their sharp ovipositor to cut tiny slits in the bark of young twigs and lays about 400 to 600 eggs within the slits. After 6 to 10 weeks of incubation, the eggs hatch into nymphs. Both parents die soon after.
The newly hatched nymphs drop to the ground and burrow about 6 to 24 in (15 to 61 cm) deep into the soil. Having strong front legs, the nymphs excavate chambers close to tree roots to obtain sap. They undergo five molts, after which the final instar nymph constructs a vertical tunnel to the surface, sheds its exoskeleton, and emerges as an adult (imago). Most species emerge during late spring to early summer.
Adults are typically eaten by a wide variety of vertebrates, including amphibians, fish, reptiles, birds, and mammals, as well as invertebrates, such as wasps, mantises, spiders, and robber flies.
While newly hatched nymphs may be eaten by ants, those that remain underground are dug up by moles. In Japan, brown bears have been observed digging up final instar nymphs of cicadas.[6]
In Australia, these insects are particularly preyed upon by the Australian cicada killer wasp (Exeirus lateritius).
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