Colour Variation in Vipera beriis. 135 



no V-shaped mark on the back of the head such as is usually 

 fairly conspicuous in Scottish specimens, neither was there 

 any indication of the dark zig-zag line which is generally 

 very prominent along the whole length of the mid-dorsal 

 aspect. In addition to this, the lateral line of regularly 

 shaped pigmented spots — also characteristic of the common 

 adder — was not to be seen. In short, the whole surface of 

 the adder, which is exposed when the reptile is lying in the 

 natural attitude, was of a uniform dark greenish brown shade 

 — so that the specimen was unique in its colour variation. 



3. Red Adders. — Eed colouring in adders is always 

 associated with the female sex. All authorities agree on 

 this point, and no common adder of the male sex, red in 

 colour, has ever been recorded. But these so-called red 

 adders are not in reality whole-coloured, inasmuch as the 

 characteristic adder markings are usually very distinctly 

 seen, and are of a brown tint. If the belly of these be 

 examined, it will be seen to be mottled grey or bluish grey 

 in colour, not red, so that the red colour is, strictly speaking, 

 the ground colour only. But there is a variety of adder 

 in which the red colour may extend all over the body, 

 including the belly, of which I am able to exhibit a speci- 

 men, and, curiously enough, in this variety the males also 

 exhibit the same colouring as the females, so that these are 

 truly whole-coloured, and red. This variety is the so-called 

 Small Ked Viper. This rare snake has, in my opinion, 

 considerable claim to be regarded as a valid species, but 

 that is a discussion on which I cannot enter now. The 

 present point is that the common adder exhibits red colour- 

 ing in the female sex only, while true, whole-coloured red 

 adders occur in both sexes of the Small Eed Viper. 



4. White Adders. — The so-called " White Vipers " may be 

 dismissed in a word or two. The term is applied to those 

 adders which show a silvery-grey body colour along with 

 very black markings, so that these adders also are not truly 

 whole-coloured. A really white adder, that is, an adder 

 which has no colour in the strict sense of the word, is 

 occasionally to be found in very old museum specimens, as 

 the result of the specimen having been bleached from long 



