326 CIVIC BIOLOGY 



Snakes Ophidia. About 140 species of snakes are native 

 to the United States, of which 17 are venomous. They are 

 all strictly carnivorous, and the nonpoisonous species are 

 beneficial or injurious, according to their foods. It is clear 

 that snakes which specialize on insects or on rats and mice 

 should merit general protection. Our little brown and green 



FIG. 159. Aquarium (24" x 18" x 12") made by student and stocked for study 



of native snakes 

 Photograph by the author 



snakes feed on insects, and the corn snake (Coluber guttatus), 

 often called the rat snake, and the gopher snake {Spilotes 

 corais couperii) are often protected about the farmsteads of 

 the South for their services in holding rodents in check. 

 The snakes that feed upon birds and birds' eggs (the black 

 snakes or the blue or green racers), those that feed on frogs 

 and toads (the garter snakes and the blowing adder, or 

 spreading adder), and those that feed on fishes (the water 

 snakes) must be studied with care and treated according to 

 local conditions and interests. 



