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Fleas are insects that form the order Siphonaptera. They are wingless, with mouthparts adapted for piercing skin and sucking blood. Fleas are external parasites, living by hematophagy off the blood of mammals and birds. Flea species include: * Cat flea (''Ctenocephalides felis'') * Dog flea (''Ctenocephalides canis'') * Human flea (''Pulex irritans'') * Moorhen flea (''Dasypsyllus gallinulae'') * Northern rat flea (''Nosopsyllus fasciatus'') * Oriental rat flea (''Xenopsylla cheopis'') Over 2,000 species have been described worldwide.〔(Fleas: What They Are, What To Do ) D. L. Richman and P. G. Koehler, University of Florida IFAS Extension. Accessed 10 December 2010〕 == Morphology and behavior == Fleas are wingless insects, 1/16 to 1/8-inch (1.5 to 3.3 mm) long, that are agile, usually dark colored (for example, the reddish-brown of the cat flea), with tube-like mouth parts adapted to feeding on the blood of their hosts. Their legs are long, the hind pair well adapted for jumping; a flea can jump vertically up to 7 in (18 cm) and horizontally up to 13 in (33 cm),〔() Crosby, J.T. What is the Life Cycle of the Flea. Accessed 6 August 2012〕 making the flea one of the best jumpers of all known animals (relative to body size), second only to the froghopper. If humans had the jumping power of a flea, a 1.8-m (6-ft) person could make a jump 90 m (295 ft) long and 49 m (160 ft) high. Researchers with the University of Cambridge in England found that fleas take off from their tibiae and tarsi (the insect equivalent of feet) and not their trochantera, or knees. It has been known that fleas do not use direct muscle power, but instead use the muscle to store energy in a protein named resilin before releasing it rapidly (like a human using a bow and arrow), with researchers using high-speed video technology and mathematical models to discover where the spring action actually happens.〔 Their bodies are laterally compressed, permitting easy movement through the hairs or feathers on the host's body (or in the case of humans, under clothing). The flea body is hard, polished, and covered with many hairs and short spines directed backward,〔(Fleas ). P.G. Koehler and F. M. Oi. Printed July 1993, revised February 2003. Provided by the University of Florida〕 which also assist its movements on the host. The tough body is able to withstand great pressure, likely an adaptation to survive attempts to eliminate them by mashing or scratching. Even hard squeezing between the fingers is normally insufficient to kill a flea. Fleas lay tiny, white, oval-shaped eggs better viewed through a loupe or magnifying glass. The larva is small and pale, has bristles covering its worm-like body, lacks eyes, and has mouth parts adapted to chewing. The larvae feed on various organic matter, especially the feces of mature fleas. The adult flea's diet consists solely of fresh blood.〔(Order Siphonaptera – Fleas – BugGuide.Net ) Accessed 28 December 2006〕 In the pupal phase, the insect is enclosed in a silken, debris-covered cocoon. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「flea」の詳細全文を読む スポンサード リンク
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