The Tetrapoda: Amphibia, Reptiles, Birds 607 



tional limbs, useless ears, and an elongate tongue which serves as an 

 accessory olfactory organ. As certain lizards also have these latter 

 features, they do not constitute absolute dififerences. 



The lizards vary so widely in their life histories, structures, food 

 habits, and mating habits that it is impossible to make any generaliza- 

 tions about them. Most of the lizards of the United States are widely 

 distributed with the greater number of species occurring in the semi- 

 arid Southwest. 



One common genus is that containing the skink, Eumeces. In the 

 East, the blue-tailed skink, Eumeces fasciatus, is very abundant, occur- 

 ring in wooded, moist areas. Mating occurs in the spring, and the 

 eggs are laid during the summer and hatch in late summer or fall. 

 The food consists of insects and other small invertebrates. During 

 the winter months, they hibernate in the ground to a depth of sev- 

 eral feet. 



Another widely distributed genus is that of the fence lizards, Scel- 

 oporus. The species of this genus have very spiny scales. The horned 

 toad, Phrynosoiua is common throughout the Southwest. This pecu- 

 liar species when molested has the ability to squeeze blood out of the 

 corner of its eyes. Both of these genera are members of the Iguanidae 

 family. Other iguanas include the common Anolis (Fig. 202,<?) the 

 chameleon of the Southeast that can change its colors so drastically that 

 its name has become a common term. In tropical America, one iguana. 

 Iguana iguana, attains a length of 6 feet and is highly valued for its 

 flesh. In the Galapagos one species of iguana attains a very large 

 size and feeds on marine algae. 



Some few lizards have completely lost their legs. These include 

 the strange worm lizards such as Rhineura floridana of Florida which 

 resembles an earthworm and the "glass snake," Ophisaurus ventralis. 

 All lizards have the unique ability to cast ofif their tails and regenerate 

 new ones. This is a protective device by which the animal is able to 

 escape, leaving its wriggling tail behind to distract its predator. This 

 ability is exceptionally well developed in Ophisaurus which has a tail 

 twice as long as its body. When attacked, Ophisaurus casts ofif this 

 long tail and looks as if it were literally flying into pieces as. the tail 

 fractures into even smaller segments. 



There is only one genus that has members which are poisonous. 

 These are the Gila monsters of the genus Heloderma (Fig. 202,;'). 

 These brightly colored "beaded lizards" occur throughout the South- 



