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BULLETIN OF THE BUREAU OP FISHERIES 



trolling mosquito breeding. 1 It is believed that the species inhabiting the smaller, 

 quiet waters of the vicinity (that is, the potential mosquito-breeding areas) are, with 

 few exceptions, represented in the collection. However, time did not permit exten- 

 sive collecting in the larger lakes. The Mississippi River was not visited and little 

 collecting was accomplished in the near-by Yazoo, Yalobusha, and Tallahatchie 

 Rivers. Pelucia and Big Sandy Creeks are the only fast-flowing streams' visited , 

 and, as explained elsewhere, collections from these streams were made only in their 

 lower courses, lying within the flat delta region. Although a somewhat different 

 fauna was met in the lower sections of these creeks, it seems highly probable that 

 their upper stretches are populated by a number of typical creek species, which, of 

 course, do not occur in the collection. 



The most favorable collecting areas for a majority of the species were furnished 

 by the many free-flowing artesian wells, near which ponds of fair size, swales, or 

 sloughs usually are found. The waters frequently support an abundant plant 

 growth, well known to be necessary as a direct source of food and even more so 

 as an indirect source. Due to the heaviness of the soil, ponds are common along 

 highways where excavations have been made in grading; and such waters, when 

 containing a moderate growth of marginal vegetation and when of fair depth, usually 

 support what might appear to be an incredible fish population, not only as to indi- 

 viduals but also as to the number of species. Most of these fish originally gained 

 ingress to these isolated waters through the rather infrequent floods to which the 

 locality is subject. The competition for food doubtless is severe in these ponds, 

 but examinations of ingested materials show a difference in feeding habits among 

 the species which would reduce such competition to a minimum. 



These ponds or lakes support an abundance of minute crustaceans, copepods, 

 in particular, furnishing an appreciable component of the diet of several species of 

 fish. A decided preference for fry and minnows is evident among a considerable 

 proportion of the local species, notably the crappies, and in such instances the top 

 minnow Gambusia is extensively preyed upon, no doubt because of its abundance 

 and comparatively unwary disposition. Upon final analysis, however, the basis 

 of the diet of the great majority of the fish collected consists of the water boatman, 

 Corixa, and to a less extent of the larvae of the midge. 



The water boatman is a rather inconspicuous little insect that gains its name 

 from its manner of progress along the surface, the long swimming legs giving it the 

 appearance of a boat propelled by oars. The adult is somewhat oval in form, 5 or 6 

 millimeters long, with mottled, brownish back and deep red eyes. The eggs are 

 deposited under water, where they are attached to plant stems (Howard, 1912, 

 pp. 273 and 274). 



The next most important source of food is the minute, wormlike larvae of the 

 midge fly. The adult midge resembles the mosquito superficially, and, like the 

 mosquito, deposits its eggs upon the surface of the water. The immature midges 

 are about 6 to 7 millimeters in length, segmented, with wedge-shaped head, and 

 translucent in color with conspicuous dark eye spots. The larvae are present in the 



1 The authors wish to extend their thanks for laboratory facilities and numerous other conveniences to Dr. M. A. Barber, 

 Dr. C. P. Coogle, and W. H. W. Komp, officers of the United States Public Health Service, all engaged at Greenwood, Miss., in 

 researches concerning malaria during the period when the collections upon which the present list is based were made. 



