North Amen'co 



INTRODUCTION 



Xorth America has a comj)aratively small but 

 ■well-known poisonous snake fauna. It includes 

 2 species of coral snakes, the closely related cop- 

 perhead and cottonmouth, and 15 species of rat- 

 tlesnakes. Most of tliese have been further di- 

 vided into subspecies so that some 39 named forms 

 are recognized. 



Poisonous snakes liave been reported from all 

 mainland states except Alaska, although they 

 have been exterminated in Maine. Only the cop- 

 perhead and 3 species of rattlesnakes have really 

 extensive ranges. Poisonous snakes in Canada 

 are restricted to comparatively small sections of 

 southern British Columbia. Alberta, Saskatche- 

 wan, and Ontario. 



Rattlesnakes ai'e known from elevations u)) to 

 11,000 feet in the southern Sierra Xevada of 

 California, to about 8,000 feet on dry, rocky 

 slopes in IVIontana, and to the tops of the highest 

 mountains in the southern Appalachians. In 

 spite of this, poisonous snakes are rare in high 

 mountains, in northern evergreen forests, and in 

 heavily farmed or urban industrial areas. 



Some species survive miexpectedly well in sub- 

 urban areas, especially in the southern United 

 States. Areas with unusually large populations 

 of poisonous .snakes include parts of the Great 

 Plains (rattlesnakes), the lower Mississippi 



Valley and Gulf Coast (rattlesnakes and cotton- 

 mouths), and the southern Appalachians (rattle- 

 snakes and copperheads). 



Snakebite is by no means rare in the southern 

 and western United States. Incidence is highest 

 in children in the 5 to 15 year age group, and 

 most bites are sustained close to home whether 

 in rural or suburban areas. Many bites result 

 from deliberate handling of venomous snakes. 

 Since 1950, there have been no more than 10 to 25 

 deaths annuallv in the United States. 



Arctic Oe t a n 



Map 2. — Section 1, North America. 



KEY TO GENERA 



1. A. Loreal pit absent (see lig. G) 2 



B. Loreal pit present (see fig. 4) 5 



2. A. Eed, black and yellow or white rings encircle the body 3 



B. Ring markings not as above NP* 



3. A. Red and yellow or Mhite body rings in contact; end of 



snout black 4 



B. Red and black rings in contact ; end of snout red, white, 



yellow or black XP 



4. A. Yellow headband followed by black ring Micnirus 



B. Yellow headband followed by red ring Micnwoides 



5. A. Tail ends in rattle _" 6 



B. Xo rattle on tail AgUstrodon 



6. A. Xine large shields on crown Si-'itrunt.s 



B. Crown shields small or fragmented into scales Ci'otalus 



♦ NP = Nonpolsonous 



37 



