. Bollettino. Storia naturale; storia naturale. Novembre, 1961 Smith: Anfibi e Rettili di Illinois 79 Tabella 19.-variazione geografica da nord a sud in lunghezza della tibia al corpo rapporti di lunghezza di Illinois Acris crepitans blanchardi. Le cifre tra parentesi sono numeri di esemplari. Caratteristica Extreme Northern Illinois (34) Nord- Central Illinois (19) Sud- Central Illinois (29) Extreme Southern Illinois (44) Gamma Gamma media gamma media Gamma media media lunghezza della tibia come per- centage della lunghezza del corpo 55.6-69.6 59,6 55.3-70.0 60,9 55.0-^9,9 61,2 55.9-67.8 61,4 di lunghezza da 1 a 3 mm. Dati per 15

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. Bulletin. Natural history; Natural history. November, 1961 Smith: Amphibians and Reptiles of Illinois 79 Table 19.—Geographic variation from north to south in tibia length to body length ratios of Illinois Acris crepitans blanchardi. Figures in parentheses are numbers of specimens. Characteristic Extreme Northern Illinois (34) North- Central Illinois (19) South- Central Illinois (29) Extreme Southern Illinois (44) Range Mean Range Mean Range Mean Range Mean Tibia length as per- centage of body length 55.6-69.6 59.6 55.3-70.0 60.9 55.0-^9.9 61.2 55.9-67.8 61.4 length by 1 to 3 mm. Data for 157 speci- mens indicate that individuals from the northern half of Illinois tend to be more ru- gose than those from the southern half. The available data on color and pattern types indicate that individuals with green, or more rarely rust-colored, middorsal marks occur with greatest frequency in the Shaw- nee Hills division and with least frequency in the Mississippi Border counties. A slight leg-length gradient is discernible from south to north, but no east-west cline is apparent. The leg-length variation is sum- marized in table 19. Habits.—This cricket frog is the most common amphibian in Illinois, and almost any wet place affords suitable habitat. Al- though Acris is a hylid, it is like a true frog in habits. The digital pads are minute, and the species is aquatic and terrestrial but not arboreal. This frog is alert and capable of making leaps astounding for its small size. It is reluctant to hibernate and it has been found active as early as February and as late as December. Its food consists of mi- nute arthropods. Although the adult cricket frogs are able to tolerate near freezing temperatures with- out becoming inactive, the breeding season is late. Singing commences about the last of April in Illinois and continues throughout the summer. The males float on the surface or sit on masses of algae while uttering their metallic "gick, gick, gick." The small e

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