The family Boidae includes the largest living snakes, but the Idaho representative of this family, the Rubber Boa (Charina bottae) is very modest in size.  The 20 genera (Pough et al. 1998) that comprise this family occupy a wide range of habitats and come in a wide range of forms.  There is also variety in the reproductive modes of species within this family.  The pythons (subfamily Pythoninae) are oviparous (egg laying), while boas (subfamily Boinae) are viviparous (live birth), this includes the native Rubber Boa.  A feature common among boas and pythons is the presence of a vestigial pelvic girdle and pelvic spurs, which are remnants of hind limb bones (Goin and Goin 1971).  Once again, the Idaho representative of this family does indeed display this trait.

The family Viperidae contains venomous species ranging from the readily recognizable rattlesnakes to the vipers of the old world.  The envenomation mechanism of members of this family are at the highest form of development (Goin and Goin 1971).  The fangs are hollow and connected to venom glands to allow the injection of venom when biting.  When the mouth is closed, the long fangs are folded up towards the roof of the mouth.  When Vipers strike, their fangs swing foward to puncture the target and allow envenomation.  The family contains 20-27 genera that are distributed across North, Central and South America, eastern Asia, Africa, and Eurasia (Pough et al. 1998).  The Idaho representative of this family is the Western Rattlesnake (Crotalus viridis).