File:Bulletin (1961) (20240300238).jpg

Title: Bulletin
Identifier: bulletin2819611963illi (find matches)
Year: 1918 (1910s)
Authors: Illinois. Natural History Survey Division
Subjects: Natural history; Natural history
Publisher: Urbana, State of Illinois, Dept. of Registration and Education, Natural History Survey Division
Contributing Library: University of Illinois Urbana-Champaign
Digitizing Sponsor: University of Illinois Urbana-Champaign

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November, 1961 Smith : Amphibians and Reptiles of Illinois 219
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Fig. 207.—A juvenile Lampropeltis triangulum triangulum from Lake County, Illinois. The groundcolor is light gray or tan; the blotches are red-brown or dark brown, heavily margined with black. of lateral spots on each side; dorsal blotches extending ventrad to scale row 2, 3, 4, or 5; venter prominently checkered with black and white; head pattern a dark chevron-shaped marking. Variation.—In Lampropeltis triangulum triangulum the average number of caudals is greater in males than in females and, sur- prisingly, males have a slightly higher blotch count on the body. The usual dimorphism in proportionate tail length and number of tail rings is not evident. Seven males and five females, exclusive of triangulum X syspila intergrades, have, respectively, 46 to 52 (av- erage 49.6) caudals and 35 to 46 (average 40.3) dorsal body blotches; 42 to 46 (aver- age 44.6) caudals and 33 to 43 (average 38.6) body blotches. Juveniles of triangulum are more brightly colored than adults; they possess black-mar- gined red, rather than brown, dorsal and lateral spots. There is some indication of a proportionately shorter tail in hatchlings. Geographic variation is summarized in table 64. Eastern milk snakes from the northernmost Illinois counties are pheno- typically triangulum. Yet in the sample from northwestern Illinois some slight influence of syspila is suggested by the number of tail rings, by the lateral rows of spots, and by the size of dorsal blotches. Intergradation of triangulum and syspila in western Illinois occurs at least as far south as Pike County, one specimen from near Pearl being approximately intermediate but closer to syspila. Specimens from Ham- ilton and Adams counties are unassignably intermediate. Intergradation in eastern Illi- nois apparently occurs in a narrower zone. Material from Tazewell and De Witt counties is closer to triangulum; Champaign and Vermilion county specimens are almost

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