FISHES IN RELATION TO MOSQUITO CONTROL 



By Samuel F. Hildebrand 



It lias been known for many years that varions species of fishes 

 prevented mosquito production when placed in small inelosures, such 

 as cisterns, fountains and pools, but only comparatively recent studies 

 and experiments have led to a fairly definite determination of the 

 species and the conditions most favorable for mosquito control in 

 larger bodies of water. Some of the species which are used for mos- 

 quito control in small artificial waters are wholly unreliable in large 

 bodies of water where a greater variety of foods is available, showing 

 that in confinement fish take foods which ordinarily are not eaten. The 

 variegated minnow {Cyprinodon variegah(s) , a strictly herbaceous 

 fish, for example, may be confined in an aquarium and fed on a diet 

 of wiggle tails and minced beef or fish and kept alive for several 

 months. It may also be placed in a pool comparatively free from vege- 

 tation, but infested with mosquito larvas, and it will live indefinitely 

 and provide mosquito control. Experiments and observations relative 

 to Mollienisia latipinna^ a minnow structurally rather close to Gam- 

 husia affinis and usually found with the latter in great abundance in 

 potential mosquito breeding areas in the lowland swamps and slug- 

 gish ditches of our coastal plains from Soutli, Carolina to Mexico, 

 have led to the conclusion, however, that the food of this species con- 

 sists almost wholly of plants and that it is worthless as an agent 

 for the control of mosquito production. 



It, therefore, is necessary, for the purpose of mosquito contriU in 

 nature, to find fishes that not only choose a habitat suitable for mos- 

 quito production but which by preference feed upon live animals. 

 They also must seek "bait" of the proper size and thej^ furthermore 

 must feed at the surface, for that is where the mosquito spends most 

 of its life in the aquatic stages. It likewise is very desirable to use a 

 fish which will reproduce under a wide range of conditions, i. e., in 

 almost any water in which mosquitoes breed, also one which multiplies 

 very rapidly. 



Ganibusia affinis, a species in which the female reaches a maximum 

 length of about 60 mm. (2% in.), the male being much smaller, very 

 admirably meets all of the requirements mentioned in the preceding 

 paragraph. It is common almost everywhere throughout the mala- 



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