MANUAL OF FISH-CULTURE. 



255 



lost. As the gills are replaced by Imigs during this perioa, it is essen- 

 tial that the tadpoles have access to land or resting-places, and it is a 

 time of peculiar difficulty in the creature's existence. When the tail 

 is almost fully resorbed, the purely aquatic life is forsaken for the 

 amphibious and the food is changed from dead to living matter, which 

 must demonstrate its living condition by motion. The peculiarly formed 

 tongue — loose behind, so that it maybe thrown out to quite a distance — 

 is covered with a viscid secretion so that the frog readily captures 

 anj' insects or small animals that approach it closely. Tadpoles are 

 commonly satisfied to wait patiently for their food, and even the adults 

 do not often search actively for food. Sexual maturity is reached in 

 about three or four years, being latest for those varieties that pass the 

 first winter in the tadpole stage. It is generally believed that frogs 

 live for 12, 15, or even 20 years. 



During the tadpole stage they furnish tempting morsels for fish, rep- 

 tiles, some mammals, and other frogs, and especially for wading birds, 

 like herons and cranes. Their defenseless condition and the shallow- 

 ness of their natural habitats at this period make them ready prey. 



Spring Frog or Leopard Frog (Bana viresceiis). 



and it is in the prevention of this wholesale destruction that man may 

 profitably intervene. In the adult frog stage the relentless pursuit by 

 birds and reptiles is continued until of the hundreds of eggs deposited 

 few become reproducing individuals. Only slight revenge for all this 

 slaughter can be taken. They may occasionally capture disabled fish 

 or small fish of sluggish habits found in the mud or on the bottom, and 

 instances are recorded of their eating snakes, toads, and young birds, 

 but insects and lower forms are their staple diet. 



DESCRIPTIONS OF MARKETABLE FROGS OF THE UNITED STATES. 



The species of frogs commonly eaten are the bullfrog {liana cates- 

 hiana), the green frog [Rana clamata), tbe spring frog {Rana rirescens), 

 and the western bullfrogs [Rana. preHosa and Rana aurora). 



The following references to their geographical distribution and brief 

 descriptions of their color and form have mainly been extracted from 

 Professor Cope's work on Tbe Batrachia of North America (Bulletin 

 No. 34, U. S. National Museum, 1889). 



