608 The Animal Kingdom 



west and into Mexico. Another unusual lizard is the "flying dragon," 

 Draco volans, of Borneo which has its sides expanded into thin mem- 

 branes. By means of these membranes, the lizards are able to glide 

 through the air. The largest of all modern lizards is the Komodo 

 dragon, Varanns komodocnsis, which lives on some islands in the 

 Dutch East Indes. These attain a length of 9 feet and some weigh 

 over 250 pounds. 



Like the lizards, the snakes are extremely varied in appearance and 

 habits, and it is quite impossible to generalize about them. All are 

 without legs and movements over the ground are accomplished by un- 

 dulations of the body or by use of broad flat abdominal scutes to which 

 the ends of the ribs are attached. The scutes are shifted forward from 

 alternate sections of the body and actually pull the body forward 

 as they catch on to the substrate. On a smooth surface, a snake is 

 very handicapped in its movements. All snakes are able to swim by 

 lateral undulations and for many aquatic forms it is the commonest 

 method of locomotion. Snakes are able to consume animals of greater 

 diameters than themselves due to their unique jaw arrangement. In 

 part this is also due to the elasticity of the throat muscles, but chiefly 

 it is due to the chain of bones that fastens the lower jaw to the skull. 

 By outward movements of this chain and by moving each half of 

 the jaw independently, large objects are swallowed. In swallowing, 

 the prey is anchored by means of the sharp curved teeth, and by 

 moving all these bony elements separately, the snake literally crawls 

 over its prey and engulfs it. 



Several times during each year, the snake sheds the outer horny 

 layer of its skin. During the periods of shedding, the transparent por- 

 tion of the fused eyelids through which the snake sees becomes opaque, 

 and the snake is temporarily blind. Snakes usually shed the outer 

 skin entirely in contrast to the lizards which shed theirs in pieces. Most 

 snakes lay their eggs in brush piles, under logs, or in soil, and de- 

 velopment takes place without any parental care. A few species retain 

 the eggs in the oviduct and the young are born alive. These latter 

 include the common garter snake, the water snakes, and the pit vipers. 



Most snakes of the United States are harmless and are members 

 of the family Colubridae. Some common members of this family 

 are the black snakes. Coluber constrictor (Fig. 202,g), which feed 

 largely on small rodents ; the bull snake, Pitnophis sayi, which is abun- 

 dant in prairie country and also feeds on rodents ; the king snakes. Lam- 



