FISHES FOR CONTROL OF MOSQUITOES. 13 



Neither the published accounts of the food of the roach nor the 

 author's notes record young stages of mosquitoes as actually found 

 in the stomachs. This result was quite unexpected, as in beginning 

 the investigation it was believed that the roach would prove one of 

 the most useful species, and it was recommended as a probable 

 mosquito destroyer during the first season. It was so regarded by 

 Prof. Smith, who wrote (1904, p. 106) : 



That this fish in its younger stages at least is an excellent mosquito control 

 is proved by observing that wherever it occurs mosquito larvse are absent, 

 except in places which it can not reach. Experimentally it was proved by 

 introducing a specimen into a water barrel swarming with wrigglers. In a 

 couple of days it had devoured practically all of the larvae and was then tJ'ans- 

 ferred to another barrel where its work was equally thorough, if a little 

 slower. As against Culex this species is excellent, as against Anopheles and 

 some other species tliat favor grassy areas it is of less account. Mr. Seal 

 seems to consider it the only fresh-water minnow worthy of attention in this 

 connection. 



In a later paper Seal (1910) again recommends it highly. 



Smith's observation that roach will partake of mosquito larvae 

 under artificial conditions has been verified by the author several 

 times on the young fishes in aquaria and rain-water barrels. At one 

 of the marsh pools on Darby Creek, below Philadelphia, a quantity 

 of water filled with wrigglers was gently poured in proximity to a 

 school of young roach, which snapped them up very quickly. On 

 another occasion, however, when a boat containing rain water swarm- 

 ing with larvae and pupae of Culex pipien^s was emptied at a sloping 

 shore of Upper Kanawaukee Lake in Palisades Park, many young 

 roach in the vicinity remained aloof, while other small fishes imme- 

 diately rushed in and quickly devoured the insects. 



Most of the stomach contents reported in Table 1 (p. 12) are from 

 fishes taken in waters where mosquitoes were breeding more or less 

 plentifully. This was notably the case at Oakes' Pond (No. 1890a) 

 and Pine Brook Bridge (No.* 1890e) in Essex County, N. J., and at 

 the Westinghouse sluice pond (No. 1881g) and the Darby Creek 

 pumping station pond (No. I88I60) of the Hog Island antimosquito 

 project in Delaware County, Pa. At Oakes' Pond on September 6 

 hundreds of young roach were swimming in schools over a shelving 

 gravelly beach and feeding on the outer side of a not very dense 

 Elodea zone about 8 feet wide, while on the shore side of this barrier 

 not a single one was seen, where in the shallow water among the 

 rather sparse emergent vegetation Anopheles larvae were present 

 generally at an average density of nearly three per dipper and in 

 places Culex pipien^s larvae at three to eight per dipper. At Pine 

 Brook Bridge several schools of young roach kept in the current both 

 of the Passaic Eiver and of a small tributary stream, while a few 

 feet away was a sheltered plant-grown offset where both Anopheles 

 and Culex were breeding in moderate numbers. At neither place 

 did the stomachs examined yield any trace of mosquito larvae. At 

 "Westinghouse pond and the pumping station pond in August, 1918, 

 large numbers of roach were taken, and in not a single case was a 

 mosquito larva found in the stomachs, although they were at hand 

 and were found in the stomachs of common sunfishes (Table 7, No. 

 18816d, p. 43) taken with the roach at the former place and in killi- 

 fishes (Table 3, No. 18816m, p. 27) at the latter. 



