PRACTICAL USE OF NATURAL ENEMIES OF MOSQUITOES. 67 



But at all events they are not lethargic like the goldfish, being on the contrary one of 

 the most active of the family, and equally at home in flowing or stagnant water. The 

 roach is always in motion, back and forth, and around and about, on a never-ending 

 patrol. 



The top-minnows would supply the deficiencies of the other two species, and in 

 combination they should very thoroughly populate any waters not already stocked 

 with predaceous kinds, and exercise an effective control. One of the great difficulties 

 in the case is that there are dozens of kinds of insect larvae besides those of the mosquito, 

 and other forms of life as well, which are natural and possibly preferred food of the 

 fishes, thus requiring an enormous population, to devour them all. 



The larvse of gnats, midges, ephemera, and other flies and insects which breed in 

 the water, as well as the many small crustaceans, afford a menu of delicacies that would 

 stagger a gourmand. The above combination of mosquito destroyers might be sup- 

 plemented by two small species of sunfish, Enneacanthus obesus and E. gloriosus, which 

 live among plants and would be a check on larvae other than the mosquito. The 

 black-banded sunfish, Mesogonistius chxtodon, would also be desirable for this purpose 

 if they were not so difficult to obtain in large numbers. One or both species of Ennea- 

 canthus can be found wherever there are aquatic plants. The above-mentioned five 

 species in combination seem to be the most suitable for pond protection of all those 

 which are known to thrive in still water and which in any degree possess the desired 

 qualities. As has been stated, the killifishes would probably be found to be unde- 

 sirable. In their natural habitat, the tidal streams and great expanses of small marsh, 

 their efficiency is unquestioned. 



There are many places at the seashore where there are swales or hollows filled with 

 grasses and bushes, which in periods of rainfall become breeding places for the mos- 

 quito, especially of Anopheles. If these places are stocked with fish, the result is 

 that when they dry up the fish perish, and the operation must be repeated after each 

 filling. 



The writer has suggested digging holes about four feet square down through the 

 turf into the sand stratum in the deepest part. Two feet is usually sufficient to secure 

 a constant water supply where the fish can exist until the hollow is again rain-filled. 

 Cyprinodon and Lucania would be desirable for such places, and they are to be found 

 everywhere in the ditches and tide pools on the flats. 



To add variety to the treatment of the subject, it might not be amiss to suggest that 

 there is a fish, Anablaps, inhabiting the fresh waters of South America, which seems 

 to be specially adapted to this purpose. To quote: "These small fishes swim at the 

 surface of the water, feeding on insects, the eye being divided by a horizontal parti- 

 tion into a lower portion for water use and a portion for seeing in the air. " 



Acting largely upon Mr. Seal's advice, Dr. John B. Smith, the state 

 entomologist of New Jersey, with Mr. Seal's help, in November, 1905, 

 brought Gamhusia affinis and Heterandria formosa from North Caro- 

 lina into New Jersey, which were distributed as follows: Eight 

 thousand in spring and natural drainage rivulets flowing into the ice 

 pond at Westville, N. J., 600 in a landlocked pond near Delanco, 600 

 in a mill pond between M^rchantville and Evesboro, 600 in landlocked 

 waters nearDelair, and 400 in ponds of the Aquarium Supply Company, 

 at Delair . In Doctor Smith' s report for the year 1 906 it was stated that 

 the experiment was to be written down a failure. Whether it w^as due 

 to the destruction of the introduced fish by black bass, pike, yellow 

 perch, and sunfish, or whether because of other enemies, or because of 

 their dislike to their changed conditions, they found their way during 



