120 BRITISH SERPENTS. 



who has observed many adders in nature will agree in 

 this general statement, that old adders are much 

 duller in colour than young ones — the young males 

 being the brightest of all, the old females the dullest 

 of all, in colouring. Adders of the same age and sex 

 in the same locality might be very nearly identical ; 

 but adders of different ages and sexes, though from 

 the same locality, will be found to exhibit great varia- 

 tion. Thus age in connection with sex must be con- 

 sidered the two main factors in the production of the 

 varying colours of adders. Locality would seem to 

 have but little influence. 



The old female adder shown is a good example of 

 what was just mentioned — viz., the disappearance of 

 the dark markings with great age. She measured 26| 

 inches in length, so there was no doubt as to her 

 maturity, and the zigzag line is discernible only for 

 an inch or two a short distance behind the neck. 

 The young male is the smallest adder I have taken 

 in the Monnow Valley, being 19f inches — equal proof 

 of his youth in that locality, where the average length 

 of males is two feet. 



All these considerations might apply to other 

 animals, but in the case of reptiles there is another 

 point to take note of, and that is sloughing. Has 

 casting the slough any effect on the colour variation ? 

 Strictly speaking, I think not. That is, the colours are 

 not different after sloughing, but they are better seen. 

 (The smooth snake is not here referred to.) The 



