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''Agkistrodon contortrix'' is a species of venomous snake endemic to North America, a member of the Crotalinae (pit viper) subfamily. The common name for this species is the copperhead. The behavior of ''Agkistrodon contortrix'' may lead to accidental encounters with humans. Five subspecies are currently recognized, including the nominate subspecies described here. ==Description== Adults grow to an average length (including tail) of . Some may exceed , although that is exceptional for this species.〔Ernst, C. H., & Barbour, R. W. (1989). ''Snakes of eastern North America''.〕 Males are usually larger than females. Good-sized adult males usually do not exceed , and females typically do not exceed.〔Palmer, W. M. (1995). ''Reptiles of North Carolina''. Univ of North Carolina Press.〕〔Stejneger, L. H. (1895). ''The poisonous snakes of North America''. US Government Printing Office.〕 In one study, males were found to weigh from , with a mean of roughly .〔Schuett, G. W., & Grober, M. S. (2000). ''Post-fight levels of plasma lactate and corticosterone in male copperheads, Agkistrodon contortrix (Serpentes, Viperidae): differences between winners and losers''. Physiology & behavior, 71(3), 335-341.〕 According to a different study, females have a mean body mass of .〔Shine, R. (1992). ''Relative clutch mass and body shape in lizards and snakes: is reproductive investment constrained or optimized?'' Evolution, 828-833.〕 The maximum length reported for this species is for ''A. c. mokasen'' (Ditmars, 1931). Brimley (1944) mentions a specimen of ''A. c. mokasen'' from Chapel Hill, North Carolina, that was "four feet, six inches" (137.2 cm), but this may have been an approximation. The maximum length for ''A. c. contortrix'' is (Conant, 1958).〔Campbell JA, Lamar WW. 2004. ''The Venomous Reptiles of the Western Hemisphere''. Ithaca and London: Comstock Publishing Associates. 870 pp., 1500 plates. ISBN 0-8014-4141-2.〕 The body is relatively stout and the head is broad and distinct from the neck. Because the snout slopes down and back, it appears less blunt than that of the cottonmouth, ''A. piscivorus''. Consequently, the top of the head extends further forward than the mouth.〔Gloyd HK, Conant R. 1990. ''Snakes of the'' Agkistrodon ''Complex: A Monographic Review''. Society for the Study of Amphibians and Reptiles. 614 pp., 52 plates. LCCN 89-50342. ISBN 0-916984-20-6.〕 The scalation includes 21–25 (usually 23) rows of dorsal scales at midbody, 138–157 ventral scales in both sexes and 38–62/37–57 subcaudal scales in males/females. The subcaudals are usually single, but the percentage thereof decreases clinally from the northeast, where about 80% are undivided, to the southwest of the geographic range where as little as 50% may be undivided. On the head there are usually 9 large symmetrical plates, 6–10 (usually 8) supralabial scales and 8–13 (usually 10) sublabial scales.〔 The color pattern consists of a pale tan to pinkish tan ground color that becomes darker towards the foreline, overlaid with a series of 10–18 (13.4) crossbands. Characteristically, both the ground color and crossband pattern are pale in ''A. c. contortrix''. These crossbands are light tan to pinkish tan to pale brown in the center, but darker towards the edges. They are about 2 scales wide or less at the midline of the back, but expand to a width of 6–10 scales on the sides of the body. They do not extend down to the ventral scales. Often, the crossbands are divided at the midline and alternate on either side of the body, with some individuals even having more half bands than complete ones. A series of dark brown spots is also present on the flanks, next to the belly, and are largest and darkest in the spaces between the crossbands. The belly is the same color as the ground color, but may be a little whitish in part. At the base of the tail there are 1–3 (usually 2) brown crossbands followed by a gray area. In juveniles, the pattern on the tail is more distinct: 7–9 crossbands are visible, while the tip is yellow. On the head, the crown is usually unmarked, except for a pair of small dark spots, one near the midline of each parietal scale. A faint postocular stripe is also present; diffuse above and bordered below by a narrow brown edge.〔 Several aberrant color patterns for ''A. c. contortrix'', or populations that intergrade with it, have also been reported. In a specimen described by Livezey (1949) from Walker County, Texas, 11 of 17 crossbands were not joined middorsally, while on one side three of the crossbands were fused together longitudinally to form a continuous undulating band, surmounted above by a dark stripe that was 2–2.5 scales wide. In another specimen, from Lowndes County, Alabama, the first three crossbands were complete, followed by a dark stripe that ran down either side of the body, with points of pigment reaching up to the midline in six places but never getting there, after which the last four crossbands on the tail were also complete. A specimen found in Terrebonne Parish, Louisiana by Ernest A. Liner, had a similar striped pattern, with only the first and last two crossbands being normal.〔 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「Agkistrodon contortrix」の詳細全文を読む スポンサード リンク
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