42 



temperature of this water was 18° C. The third locality was an old 

 canal bed so nearly dried out after a season of drought that the water 

 lay in rather small puddles. In this case the water was very foul and 

 alga3 of the genus Lyngbya were present. The temperature of this 

 water was 25° C, and the conditions were those of extreme stagnation. 

 The first locality was discovered by the writer in company with Mr, 

 Pratt and the second and third were found by Mr. Pratt, Later, the 

 writer in company with Mr, Busck and Hospital Steward Smith, found 

 empty pupa skins of xi. quadrim.aculatus in a dried up surface pool at 

 the Washington Barracks, at a time when malaria was very prevalent 

 among the troops. I am informed by Dr. Thayer, of Baltimore, that 

 Dr, Lazear found A. punctipennis breeding in a stone quarry near 

 Baltimore, in the summer of 1899, Ross found in India that while the 

 species of Culex generally bred in vessels of water around the houses, 

 the species of the genus Anopheles l)i'ed in small pools of water on 

 the ground. This point w^as made the subject of a special investiga- 

 tion by the expedition of the Liverpool School of Tropical Medicine 

 to Sierra Leone. While Culex larvae w^ere to be seen in almost every 

 vessel of water or empty gourd or flowerpot in which a little rain 

 water had collected, in only one case were Anopheles larva? found in 

 such receptacles. On the other hand, they occurred in about 100 

 small puddles scattered throughout the city of Freetow^n — puddles 

 mostly of a fairly permanent description, kept filled by the rain, and 

 not liable to washing out during heavy showers. It was noticed also 

 that the larvEe seemed chiefly to feed on green water weed. 



In the interesting and important paper by Dr, J, W. W. Stephens 

 and Mr, S. R. Christophers entitled ''The distribution of Anopheles 

 in Sierra Leone," published in the report of the malarial counuittee of 

 the Royal Society, July 6, 1900, it is stated that at Freetown not 

 only do the larvte of Anopheles exist in the small pools in the rocks, 

 but also in the pools by the sides of streams and in certain small 

 drains, and that in the dry season, in the absence of the rock pools, 

 Anopheles l)reeds freely in streams and drains; also, in the dry season, 

 the adults exist in most parts of the town in dwellings, especially in 

 overcrowded native huts and native quarters, ready to lay their eggs 

 when pools appear. It is interesting to note, from this latter obser- 

 vation, that the authors of the paper recommend the destruction of 

 dirty huts and the prevention of excessive overcrowding. Outside of 

 the city, in the "bush," Anopheles larvre were present throughout the 

 whole district. In the mountain streams, wherever there were suitable 

 pools, multitudes of lai'vse existed. In tracing the mountain streams, 

 occasionally for a half mile or so, they found no larva% but then a 

 rock pool occurred, and there they were again found in numbers. At 

 Songo and Mabang they were able to detect Anopheles larvse in the 

 swamps. They were not present in the main swamp water on account 



