14 V. S. BUREAU OF FISHERIES. 



SO far tested have reacted favorably to infection and are being used 

 in the artificial propagation of this mussel. 



The food, size, habits, and habitat of Lepoinis humiUs in Louisiana 

 suggest that the species may be of considerable importance as a 

 natural enemy of immature mosquitoes. 



SUMMARY. 



Lepomis JiumiUs, the orange-spotted sunfish, has a natural distribu- 

 tion throughout the Mississippi drainage. It is found particularly 

 in lowland waters and has been studied in typical habitats in Iowa 

 and Louisiana. Its usual environmental associates are especially the 

 white crappie, the green sunfish, and the golden shiner. In Loui- 

 siana Gambusia is usually found in abundance with the sunfish. The 

 sexes of the orange-spotted sunfish are easily determined during the 

 breeding season by the color, color pattern, and differences in outline. 

 The male at this season is very brilliantly colored; the female is much 

 duller. 



The breeding season varies in lengih for fish of Iowa and Loui- 

 siana. The period of mating is a protracted one, lasting for Loui- 

 siana fish nearly 5 months and for those of Iowa about 10 weeks. 

 The breeding season is prolonged, especially through the attainment 

 of sexual maturity by certain fish in their second growth year. 

 Growth of Louisiana fish indicated by scale examinations is some- 

 what faster than that of Iowa fish. Early born fish may attain 

 sexual maturity late in their second growth year. The great ma- 

 jority of orange-spotted sunfish lay their first eggs at the beginning 

 of the third year. There is a normal retardation of growth as the 

 sunfish reaches sexual maturity. The grow^th of the species, how- 

 ever, continues at a rapid rate through the third and fourth growth 

 years. Lepomis humilis reaches a length of about 4 inches. 



The nest of Lepo^mis humilis observed in Iowa is a small bowl- 

 shaped excavation made in gravel in from 12 to 36 inches of water. 

 Its habitat where observed in the delta country of Louisiana 

 furnishes no gravel for nest building and eggs are probably laid on 

 the mud. Mating is promiscuous, and the eggs are protected from 

 spawn-eating fishes by the pugnacious male, which remains on the 

 nest fanning the eggs with its fins until the fry emerge. The number 

 of eggs laid by each female varies with its size and age. The maxi- 

 mum number of eggs observed was 4,700 for a female 10.5 cm. long, 

 taken in June; the smallest egg-bearing female measured 3 cm. 



The food of Lepomis JimniUs is made up primarily of crustaceans 

 and insect larA^se. In these items the diet of the sunfish closely resem- 

 bles that of the recognized mosquito-larva? destroyer, Gambusia. 



The value of the orange-spotted sunfish lies in its importance in 

 the economy of the fishpond. It transforms the microscopic fauna 

 into its own flesh, which in turn may serve as the food of larger 

 carnivorous fishes of acknowledged sport and food value. Data are 

 presented indicating the usefulness of this sunfish in the artificial 

 pond culture of the large-mouth black bass. Other data presented 

 suggest the prolificness of the fish. 



The value of Lepomis humilis as a test fish in pollution and other 

 similar studies, in the biology of the fresh-water mussel, and in pos- 

 sible usefulness as a mosquito-control agent is discussed. 



