THE ADDER. 



93 



half an incli to an inch and a half longer than the 

 males in the same place. Thus in South Hereford- 

 shire adult male adders average 24 inches, adult 

 females 2o| inches in length. All the exceptionally 

 long specimens that have come under my own 

 notice have been females, but it should be men- 



Fio. 20. — Smooth Newts. 



tioned tliat Mr Boulenger did not find this difference 

 to be constant in a series he examined. 



Length of tail. — This is a constant sexual differ- 

 ence, the tail in the males being invariably longer 

 than in the females. Speaking generally, the male 

 adder's tail is 3 inches long, the female's tail 2J 

 inches. But the leno;t]i of the tail of course varies 



