<P> The common adder is found in different terrains, habitat complexity being essential for different aspects of its behaviour . It feeds on small mammals, birds, lizards, and amphibians, and in some cases on spiders, worms, and insects . The common adder, like most other vipers, is ovoviviparous . Females breed once every two or three years, with litters usually being born in late summer to early autumn in the Northern Hemisphere . Litters range in size from three to 20 with young staying with their mothers for a few days . Adults grow to a total length (including tail) of 60 to 90 cm (24 to 35 in) and a mass of 50 to 180 g (1.8 to 6.3 oz). Three subspecies are recognized, including the nominate subspecies, Vipera berus berus described here . The snake is not considered to be threatened, though it is protected in some countries . </P> <P> The name "adder" is derived from nædre, an Old English word that had the generic meaning of serpent in the older forms of many Germanic languages . It was commonly used in the Old English version of the Christian Scriptures for the devil and the serpent in the Book of Genesis . In the 14th century, "a nadder" in Middle English was rebracketed to "an adder" (just as "a napron" became "an apron" and "a nompere" changed into "an umpire"). </P> <P> In keeping with its wide distribution and familiarity through the ages, Vipera berus has a large number of common names in English, which include: </P> <Dl> <Dd> Common European adder, common European viper, European viper, northern viper, adder, common adder, crossed viper, European adder, common viper, European common viper, cross adder, or common cross adder . </Dd> </Dl>

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