PISCES 



245 



The true eels {Anguillidae) are found in fresh and salt water. 

 They migrate upstream to the headwaters of fresh water rivers and 

 live there until at maturity they pass down to the sea to spawn. 

 It is only recently that their habits became fully known. (See page 

 264.) 



Fig. 125. A, pike. B, pickerel. C, muskellunge. (Courtesy of Slingerland-Com- 



stock Publishing Co.) 



The pikes {Esocidae) (Figure 125, A^ B, C) include the pickerel, 

 Esox lucius, which is a serious enemy of other more important 

 food fishes, and also captures frogs and small birds. The muskel- 

 lunge {Esox masquinongy) is a hard fighting food fish reaching a 

 weight of one hundred pounds and a length of six feet. 



The mummichogs {Poecilidae) include the salt water minnow, 

 Fu7idulus hetej-oclitus, which is not only extremely valuable in 

 mosquito extermination on the northern salt marshes of the U. S., 

 but is of great use in experimental embryology. (Figure 126, A 

 and B.) 



The top minnow {Gambusia affinis) is of great Importance in 

 the extermination of the larvae of Anopheline mosquitoes. They 



