642 



OPHIDIA 



black in the males through extension of the black markings, 

 in the females through darkening of the ground-colour. Males 

 are usually distinguishable from females by darker, deep black 

 markings and lighter ground-colour. The females are mostly 

 larger than the males. The largest specimen in the British 

 Museum measures 700 mm. = 28 inches, but a viper 2 feet 

 long may be considered a very large specimen. The Common 

 Viper has a wide range, from Wales to Saghalien Island, and from 

 Caithness to the north of Spain. It ascends the Alps to a con- 

 siderable altitude, up to 6000 feet. J. Blum 1 has published an 

 elaborate statistical account of the Viper in Germany, un- 

 fortunately confining himself strictly to the political frontiers. 



According to the map 

 attached to his work, the 

 Viper is common all over 

 Germany with the excep- 

 tion of South - Western 

 and parts of Middle Ger- 

 many. It is absent in 

 Alsace, the Bavarian Pala- 

 tinate, Ehenish Prussia, 

 Hesse, the northern half 



of Baden, Wiirtemberg, 

 and Franconia, countries 



FIG. 174. Skin of Viper. x 1. (From White's 

 History of Selborne. ) 



which, speaking broadly, 



have a warm subsoil, composed of Red Sandstone and Basaltic 

 formation. As a rule the Viper prefers heaths, moors, and mixed 

 woods with sunny slopes. Brambles, clumps of nettles, hedges, 

 the edges of little copses, heaps of stones, are favourite places of 

 retreat, affording shelter, holes, and the vicinity of mice, which 

 form its chief sustenance. At harvest-time it is often found in 

 cornfields, and it frequently hides in the sheaves. Vipers are 

 fond of basking on certain spots, on the top of a stone, the 

 stump of a tree, or a patch of sand : a shower of rain or even 

 passing clouds drive them back into their holes. They are 

 eminently nocturnal, when they regularly " beat " their district, 

 biting and paralysing their prey before swallowing it. A fire 

 kindled at night is sure to draw vipers near ; the same applies 

 to other vipers, for instance Cerastes, which appears in perplexing 

 1 Verbreitung der Kreuzotter in Deutschland. Frankfurt a. M. 1888. 



