In snake species with a blotched dorsum, blotch fusion is one of the most commonly observed pattern aberrancies. This is particularly true for rattlesnakes (Viperidae: Crotalus and Sistrurus). Complete or partial blotch fusion has been reported in 47 individual rattlesnakes, across 16 taxa. Illustrations, descriptions, or both have been published for C. adamanteus (Antonio and Barker, 1983; Jensen et al., 2008), C. atrox (Nickerson and Mays, 1968; Simons, 1986), C. durissus terrificus (Amaral, 1932), C. horridus (Gloyd, 1935; Dundee, 1994; Bechtel, 1995), C. oreganus concolor (Schuett and Kraus, 1982), C. ravus (Rubio, 1998), C. scutulatus (Gloyd, 1958; Nickerson and Mays, 1968), C. viridis (Gloyd, 1935; Ashton et al., 1999; Hammerson, 1999), S. catenatus (Oldham, 1985; Bechtel, 1995), and S. t. tergeminus (Lardie and Lardie, 1976; Irwin, 1979; Buerer and Geluso, 2014). Passing mention of the morph can be found for C. aquilus, C. lepidus morulus, C. o. oreganus, C. o. viridis, C. ruber, and C. stephensi (Klauber, 1972). Several captive-bred C. o. oreganus X C. scutulatus hybrid siblings also exhibited partial blotch fusion (Cook, 1955). While at times superficially similar to the blotch-fusion aberrancy, we consider the “patternless” or “striped morph” aberrancy reported in C. atrox, C. adamanteus, C. durissus terrificus, C. horridus, C. ruber, C. scutulatus, and C. viridis (Amaral, 1932; Gloyd, 1958; Nickerson and Mays, 1968; Shupe, 1977; Irwin, 1979; Karges, 1979; Holmback, 1985; Yancey et al., 1997; Rubio 1998) to be a different, unrelated abnormality. The complete lack of lateral blotches/stripes, coupled with the pristine appearance of the faint dorsal stripe (when present) distinguishes this morph from the blotch-fusion aberrancy. Complete or partial blotch-fusion is not unique to crotalid snakes. It has also been documented in five species of Central and South American viperids: Bothriechis schlegelii, Bothrops alternatus, B. cotiara, B. jararaca, and B. pauloensis, (Amaral, 1932; Machado, 1945; Lema, 1960; Campbell and Lamar, 2004; Barrio- Amorós, 2015). And in four species of North American colubrids: Lampropeltis c. calligaster (Smith, 1961; Anderson, 1965; Cox, 1972; Ashton, 1973; Dyrkacz, 1982; Bechtel, 1995), Pantherophis emoryi (Gloyd, 1935; Bechtel, 1995), P. guttatus (Bechtel and Bechtel, 1978), and P. obsoletus (Werler, 1951; Bechtel, 1995). A similar type of pattern aberrancy, the partial transformation of transverse bands into longitudinal stripes, has been reported in Agkistrodon contortrix mokasen (Gloyd, 1958), unidentified subspecies of A. contortrix (Bechtel, 1995), Cemophora coccinea (Bechtel, 1995), Lampropeltis alterna (Tryon, 1979), L. annulata (Williams, 1978), L. triangulum (Gehlbach, 1962; Williams, 1978), and Rhinocheilus l. lecontei (McCrystal and Ivanyi, 2005; Bechtel, 1995). Two additional species, Pituophis c. catenifer and L. getula californiae, have populations that frequently include completely striped color morphs, instead of the species’ typical blotched or banded pattern, respectively (Klauber, 1939; Banta, 1964). Detailed study of the underlying cause of blotch fusion has been published for two colubrid taxa. In Pantherophis guttatus, Bechtel and Bechtel (1978) presented evidence that partial dorsal blotch-fusion is attributable to a recessive genetic mutation. In Pituophis c. catenifer, available evidence from controlled captive breeding also points to a Mendelian recessive-dominant mechanism—but with striping dominant to blotching (Bechtel and Whitecar, 1983). The mechanism(s) Herpetology Notes, volume 8: 331-334 (2015) (published online on 16 June 2015) Temperature Shock as a Mechanism for Color Pattern Aberrancy in Snakes Adam G. Clause 1, * and Richard N. Becker 2 1 Warnell School of Forestry and Natural Resources, University of Georgia, Athens, Georgia 2 10711 Gay Road, Wilton, California * Corresponding author e-mail: adamclause@gmail.com