Cicada molting

Cicada outer shell (moult)

Cicada outer shell (moult)

Cicada molting

Cicada molting

A cicada is any of several insects of the order Hemiptera, suborder Auchenorrhyncha, in the superfamily Cicadoidea, with small eyes wide apart on the head and transparent, well-veined wings. Cicadas live in temperate to tropical climates where they are one of the most widely recognized of all insects, largely due to their large size and remarkable (and often inescapable) acoustic talents. Cicadas are sometimes called "locusts", although they are unrelated to true locusts, which are a kind of grasshopper. Cicadas are related to leafhoppers and spittlebugs.

Taxonomy
There are many thousands of species of cicadas, arranged into two families: Tettigarctidae (treated elsewhere) and Cicadidae. There are two extant species of Tettigarctidae, one in southern Australia, and the other in Tasmania. The family Cicadidae is subdivided into the subfamilies Tettigadinae, Cicadinae and Tibicininae, and they occur on all continents except Antarctica.

The largest cicadas are in the genera Pomponia and Tacua. There are some 200 species in 38 genera in Australia, about 450 species in Africa, about 100 in the Palaearctic and exactly one species in England, the New Forest Cicada (Melampsalta montana), which is widely distributed throughout Europe. There are about 150 species in South Africa.

Most of the North American species are in the genus Tibicen—the annual or dog-day cicadas (named after the "Dog Days" because they emerge in late July and August). The best-known North-American genus is Magicicada, however. These periodical cicadas have an extremely long life cycle of 13 or 17 years and emerge in large numbers. Another American species is the Apache Cicada (Diceroprocta apache).

38 species from five genera populate New Zealand, and all of the species are endemic to New Zealand and the surrounding islands (Norfolk Island, New Caledonia).

Description
Adult cicadas, sometimes called Imago|imagines, are usually between 2 and 5 cm (1 to 2 inches) long, although there are some tropical species that reach 15 cm (6 in), e.g. Pomponia imperatoria from Malaysia. Cicadas have prominent eyes set wide apart on the sides of the head, short antenna (biology)|antennae protruding between or in front of the eyes, and membranous front wings. Desert cicadas are also one of the few insects known to cool themselves by sweating, while many other cicadas can raise their body temperatures voluntarily to around 40°C, even when the air temperature is only 18°C.

Male cicadas (and only males) have loud noisemakers called "tymbals" on the sides of the abdominal base. Their "singing" is not stridulation as in many other familiar sound-producing insects like crickets (where two structures are rubbed against one another): the tymbals are regions of the exoskeleton that are modified to form a complex membrane with thin, membranous portions and thickened "ribs". They rapidly vibrate these membranes with strong muscles, and enlarged chambers derived from the tracheae make their body serve as a resonance chamber, greatly amplifying the sound. Some cicadas produce sounds louder than 106 dB (SPL), among the loudest of all insect-produced sounds. (This amazing sound has frequently inspired haiku poets in Japan to write about them.) They modulate their noise by wiggling their abdomens toward and away from the tree that they are on.

Only males produce the cicadas' distinctive sound. Both sexes, however, have tympana, which are membranous structures used to detect sounds; thus, the cicadas' equivalent of ears.

Life cycle
Magicicadas molting
After mating, the female cuts slits into the bark of a twig and deposits her eggs there. She may do so repeatedly, until she has laid several hundred eggs. When the eggs hatch, the newborn nymphs drop to the ground, where they burrow and start another cycle. Most cicadas go through a life cycle that lasts from two to five years. Some species have much longer life cycles, e.g. the Magicicada goes through a 13- or even 17-year life cycle. These long life cycles are an adaptation to predation, as a predator could not regularly fall into synchrony with the cicadas. 13 and 17 are prime numbers, so while a cicada with a 15-year life cycle could be preyed upon by a predator with a 3- or 5-year life cycle, the 13- and 17-year cycles allow them to stop the predators falling into step.

Most of this time, the animals spend underground as nymphs at depths ranging from about 30 cm (1 ft) up to 2.5 m (about 8½ ft). The nymphs feed on root juices and have strong front legs for digging.

In the final nymphal instar, they construct an exit tunnel to the surface and emerge. On a nearby plant, they moult one last time and emerge as an adult. When they moult, they shed their skins, and the abandonded skins can often be found left on trees, still clinging to the bark.

This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Cicada".

Cicada molting

Cicada molting

Cicada molting

Cicada molting

Cicada molting