FISHES AND THE MOSQUITO PROBLEM. 835 



great need is that there shall be enough mosquito eaters to consume all the 

 other food that occurs and all the mosquitoes as well. And this means enormous 

 numbers of fishes. What this involves is yet to be determined. We have no 

 adequate conception of it. 



While, as has been stated, all fishes have some measure of usefulness, if 

 only in the way of deterrent effect, there are only a few species likely to be found 

 in waters in which mosquitoes breed, and especially where Anopheles breeds. 

 The most important of these are: The goldfish, which are introduced; several 

 species of Fundulus (the killifishes) and allied genera; three or four species of 

 sunfish; the roach or shiner; and one or two other small species of cyprinoids. 

 In addition, there are a few sluggish and solitary species like the mud-minnow 

 (Umbra) and the pirate perch (Aphredoderus), which live among plants. The 

 sticklebacks have been mentioned in this connection, but the Atlantic coast 

 species are undoubtedly useless for the purpose, being bottom feeders, living in 

 the shallow tide pools and gutters, hidden among plants, or under logs and 

 sticks at the bottom, where they find an abundance of other food. 



In the salt marshes there are myriads of killifishes running in and out and 

 over them with each tide, while countless numbers of other and smaller genera, 

 such as Cyprinodon and Lucania, remain there at all stages of the tide. So 

 numerous and active are all these that there is no possibility of the develop- 

 ment of a mosquito where they have access. Of the killifishes two species, 

 heteroclitus and diaphanus, ascend to the farthest reaches of tide flow, but it is a 

 question as to whether they would prove desirable for the purpose of stocking 

 landlocked waters, since they are much like the English sparrow, aggressive 

 toward the more peaceable and desirable kinds. Even Cyprinodon, which would 

 seem to be a valuable small species for the purpose, is viciously aggressive 

 toward goldfish and no doubt all other cyprinoids. It is characteristic of all 

 killifishes that they must be kept by themselves in aquaria. They are the 

 wolves and jackals of the smaller fishes. 



As a destroyer of A nopheles the writer has for several years advocated the 

 use of Gambusia affinis, a small viviparous species of fish to be found on the 

 south Atlantic coast from Delaware to Florida. A still smaller species of another 

 genus, Heterandria formosa, ranging from ^4 inch to K inch in length for 

 the males to i inch or i yi inches in length for the females, is generally to be 

 found with Gambusia and is of the same general character. Both of these 

 species are known as top minnows from their habit of being at the surface 

 and feeding there; the conformation of the mouth, the lower jaw projecting, 

 is evidence of such feeding habit. Both are to be found in great numbers in 

 the South in the shallow margins of lakes, ponds, ar^d streams in the tide-water 

 regions wherever there is marginal grass or aquatic or semiaquatic vegetation to 



