REPTILIA 257 



residual instinct dating back to the arboreal period of man's ancestry, 

 we cannot say. Tliis much should be said for the snakes, however, 

 that most of them deserve nothing but kindly treatment, since they 

 are far more beneficial than many animals that have a much better 

 reputation. It would appear that the few venomous snakes have 

 given a bad name to the whole group. 



Snake Venom. — Many snakes, but a small percentage of the 

 whofe group, are more or less venomous, but as a rule they are much 

 less deadly than they are supposed to be. Unfortunately there is 

 no simple criterion for distinguishing the poisonous snakes from 

 the non-poisonous. One merely has to acquaint himself with the 

 habitat and appearance of the various snakes native to the country 

 in which he resides or in which he is sojourning. The poison is 

 secreted in a pair of enlarged labial glands, homologous with the 

 parotid glands of the mammals. A duct leads from these glands 

 to the hollows of the paired tubular fangs. The strike of the snake 

 presses upon the gland and causes the poison to exude from the tip 

 of the fang into the deepest part of the wound. Fortunately for 

 us there are only five kinds of venomous snakes in the United 

 States: coral snakes, water moccasin, copperhead, rattle -snakes, and 

 opisthoglyphs. 



There are two species of coral snakes both belonging to the genus 

 Elaps; both are native to the Southern States. They are extremely 

 conspicuous owing to the vivid contrasting bands of red, black and 

 yellow, another example of the so-called warning coloration. The 

 coral snakes are said to be extremely poisonous,' but their biting equip- 

 ment is so constructed that they cannot open the mouth wide enough 

 to bite a human being; so they may be set aside as harmless, so far as 

 man is concerned. 



The water moccasin {Andstrodon pisdvorus), the so-called 

 "cotton mouth," is a large, heavy, aquatic species that reaches a 

 length of five or six feet. It is really a species of rattle-snake without 

 a rattle. This snake has the reputation of being by far the most 

 venomous of all North American snakes, but it is very unusual for a 

 human being to be bitten by it, and fatal cases are exceedingly rare. 



The copperhead {Andstrodon contortrix) ranges from Massa- 

 chusetts to Florida and west to Texas. It also is a species of rattler 

 without any rattle. 



The true rattle-snakes comprise a number of species belonging to 



