FISHES FOR CONTROL OF MOSQUITOES. 19 



swarming with Infusoria. When first discovered, on July 7, there 

 was excessively heavy breeding (counts not recorded) of Culex 

 pipiens. There were larvae of all sizes, egg boats, and many pupae, 

 besides a few Anopheles. The bottom and water were thoroughly 

 explored vfith seine and dip net and not a single fish found. Tad- 

 poles, aquatic Hemiptera and Coleoptera, chironomid larvae, cope- 

 pods, Asellus, Physa, and Stylaria were plentiful, and there were 

 some insect larvae, amphipods, ostracods. Hydra, and a few Glossi- 

 phonia, Erpobdella, and Planorbis. Chironomid larvae were espe- 

 cially abundant in the soft bottom mud. Outside of the hole 

 mosquito larvae were equally plentiful in little pools among the tus- 

 sock ferns, but there was no breeding whatever on the brook side and 

 only moderate breeding aiiiong the plants on the bay side of the pool. 



On July 11 opposite openings were made in the banks, placing the 

 pool in communication with the brook on one side and the bay on the 

 other and inducing a current from the former to the latter. On the 

 morning of the following day the use of the dip net immediately 

 demonstrated the presence of mud minnows in the pool. The stomachs 

 (Table 2, No. 2334, p. 16) of these were well filled and all contained 

 larvae of Culex pipiens and one of them no less than 12 entire pupae 

 of the same species. These, with two Corethra larvae, comprised 

 about 35 to 40 per cent of the entire stomach contents, the remainder 

 being 12 per cent of the larvae and pupae of other insects, chiefly 

 chironomids and mayflies, about the same of entomostracans, and 

 small amounts of ooze, plant remains, and miscellaneous matter, in- 

 cluding one leech. It will be noted that these newly admitted mud 

 minnows accepted animal food in the approximate order of its abun- 

 dance and accessibility. 



On July 15 only two mud minnows were secured, along with a 

 few sunfishes. They were taken in the afternoon and their stomachs 

 (Table 2, No. 2353a) contained little. Two Culex larvae were found 

 in one, none in the other, most of the food being chironomid larvae, 

 some larvae of other insects, and a quantity of mud and plant re- 

 mains. Ten water samples yielded a total of 30 larvae and 1 pupa 

 of Culew pipiens, an average of three, and a very striking decrease 

 in four days. In the undisturbed small pools among the tussocks 

 every sample yielded 28 to 30 or more larvae besides some pupae and 

 egg boats. 



On July 24 two mud minnows were again taken from the pool, 

 together with two sunfishes and a large number of young minnows 

 (Notropis) . On this date mosquito breeding had fallen to an average 

 of less than one-third larva per sample, but in the check pools re- 

 mained undiminished. None of the stomachs of any of the fishes 

 examined yielded undoubted mosquito remains. The collection was 

 made close to noon and the food (Table 2, No. 2359b) of the mud min- 

 nows was in an advanced stage of digestion. It consisted chiefly of 

 fragmented insect remains, including many chironomid larvae, many 

 copepods, and much of the mudlike material containing filamentous 

 algae, protozoans, protophytes, plant debris, and sand grains. In the 

 intestines were some broken hairs that may have come from mosquito 

 larvae. 



On July 30 three stomachs (Table 2, No. 2363a) contained one 

 Culex pipiens, many chironomid larvae in tubes, large numbers 

 of a large Cyclops, and some insect remains. Ten samples yielded 



