AMPHIBIA 



319 



FIG. 151. Common tree frog 



Photograph by Millett T. 

 Thompson 



to frogdom in a pond 30 feet by 15, having a depth of 2 feet of water." 

 As eggs of leopard frogs, pickerel frogs, and wood frogs can usually be 



gathered in any desired quantity, this would 

 indicate almost unlimited possibilities of 

 live-food production. 



In addition to their uses, actual and 

 potential, as insect traps, frogs have com- 

 mercial values which threaten their exter- 

 mination in many localities. In some places 

 small ones bring from $1 to $2.50 per 100 

 for fish bait. The frog is the animal most 

 commonly used for laboratory study the 

 world over ; frogs used for this purpose 

 bring from 50 cents to $3 per dozen. More- 

 over, while they were rarely used for food 

 a few years ago, frogs' legs have now be- 

 come a well-known delicacy. "The meat 

 is white, delicate, and very wholesome and 

 palatable." Hence catching frogs for mar- 

 ket often yields good profit, and it affords a mildly humorous form of 

 outdoor sport. As these values come to be recognized, valuable species 

 can be protected by closed seasons (from the opening of spring until 



after they spawn), local . , 



waters can be kept stocked 

 to their full capacity, and 

 an abundant crop can be 

 secured each year. 



Some special problems. 

 1. In a pond stocked with 

 bullfrogs, how can we feed 

 so as to prevent cannibal- 

 ism and thus secure the 

 greatest number of large 

 specimens from a given 

 area? 



2. How can the largest number of toads be reared from a pool a foot 

 square and a foot deep? (We have one record of 3938 from April to 

 August ; the main foods were algse, dog biscuit, and fresh fish.) 



3. Are toads being exterminated from agricultural districts by drain- 

 ing their breeding pools, by farm animals, and by the operation of farm 



FIG. 152. Pair of spotted salamanders 

 Photograph by Millett T. Thompson 



