Cicada

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{{Taxobox | color = pink | name = Cicada | image = Tibicen_linnei.jpg | image_width = 250px | image_caption = Annual Cicada Tibicen linnei | regnum = Animalia | phylum = Arthropoda | classis = Insecta | ordo = Hemiptera | subordo = Homoptera | familia = Cicadidae | familia_authority = Westwood, 1840 | subdivision_ranks = Genera | subdivision = Many. }} A cicada is any of several insects of the order Hemiptera, suborder Cicadomorpha or Auchenorrhyncha, with small eyes wide apart on the head and transparent well-veined wings. Cicadas live in temperate to tropical climates. Cicadas are sometimes called "locusts", although they are unrelated to true locusts. They are related to leafhoppers and spittlebugs.

1 Taxonomy
2 Description
3 Life cycle
4 See also
5 External links

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Taxonomy

There are many thousands of species of cicadas, arranged into two families, Tettigarctidae and Cicadidae. There are two extant species of Tettigarctidae, one in southern Australia, and the other in Tasmania. The Cicadidae is subdivided into the subfamilies Tettigadinae, Cicadinae and Cicadettinae, and they occur on all continents.

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

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Description

Adult cicadas, sometimes called 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. the Pomponia imperatoria from Malaysia. Cicadas have prominent eyes set wide apart on the sides of the head, short antennae protruding between or in front of the eyes, and membranous front wings. Deseert 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 have loud noisemakers called "tymbals" on their sides. Their "singing" is actually a kind of stridulation: they vibrate these membranes with strong muscles; their body serves as a resonance body greatly amplifying the sound. Some cicadas produce sounds louder than 106 dB. (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.

The fact that only males produce the cicadas' distinctive sound prompted Xenophon to remark "Blessed are the cicadas, for they have voiceless wives."

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Life cycle

Image:Snodgrass Magicicada septendecim.jpg Image:20040515 083441 1 crop2.jpg

Most cicadas go through a life cycle that lasts between 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 adaption to predation, as a predator could not regulary fall into synchrony with the cicadas. Another feature of these life cycle is that 13 and 17 are prime numbers. A cicada with a 15-year life cycle could be preyed upon by a predator with a 3- or 5-year life cycle, but 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 molt one last time and emerge as an adult. When they molt, they shed their skins, and the abandonded skins can often be found left on trees, still clinging to the bark.

Image:Exit tunnels of Cicada A.jpg	Image:Exit tunnels of Cicada B.jpg	Image:Exit tunnels of Cicada C.jpg
Exit tunnels of Cicada (Japan)

Only the males have tymbals and "sing" to attract females. 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.

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