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innovations, ingenious methods, more efificient tools, etc., to meet 

 the requirements of the sudden exigency, to the great benefit of the 

 operations as a whole. The general principles of mosquito control 

 consist primarily of drainage, where the water can be disposed of, and 

 oiling, where it must remain ; both metliods are aimed at the Anophe- 

 line larvae, little, if any, attempt having been made to deal with the 

 adult mosquitos. 



The three mosquitos to be considered as vectors of malaria in 

 North America are : — Anopheles quadrimaculahis, A. 'pundi'pennis, and 

 A. crucians, the first of which is undoubtedly the most important, 

 since it enters houses to feed more readily than will either of the other 

 species. Whether it actually prefers human blood to that of domestic 

 animals is imcertain, whereas the other two species exhibit a definite 

 preference for the latter. It breeds in natural waters in preference 

 to artificial containers, mainly in ponds, swamps, puddles, lakes, etc., 

 and is very seldom found in running water, while a small amount of 

 sewage or of chemical or other contamination will effectually prevent 

 breeding. A. punctipennis should rank first in point of numbers and 

 general distribution. Its breeding places are the same as those of 

 A. quadrimaculatus, with, in addition, streams or ditches of slowly 

 running water, and it also seems to be able to stand more contamina- 

 tion than A. quadrimaculatus. Although it is known to transmit 

 malaria under laboratory conditions, the impression exists that in 

 nature it is relatively unimportant as a yector of malaria. The final 

 determination of this point would effect the saving of an immense 

 amount of money now being spent, perhaps needlessly, on the eradica- 

 tion of this species. A. crucians is generally less common than the 

 other two, and is found in the most restricted localities, often in brackish 

 waters, or waters contaminated with chemicals, where, in suitable 

 places, it may be extremely abundant. Its importance as a vector 

 of malaria is a relatively unknown quantity, for though it is known 

 to harbour at least one of the malaria parasites, it shows a preference 

 for the company of domestic animals rather than that of man. 



The most reliable and most permanent control is effected by drainage, 

 which includes the cleaning of ditch banks and the removal of debris. 

 Temporary puddles can probably be best dealt with by oiling, and 

 roadside ditches can usually be ditched without much difficulty. 

 Borrow-pits may either be drained or oiled according to their depth, 

 and old wells, cisterns and the like may be filled or oiled or treated 

 with chemicals, attempted drainage being seldom advisable. Eeal 

 drainage problems arise in the matter of ponds, lakes and swamps, 

 and these must be dealt with according to the sources of water. Rain- 

 water ponds and swamps can be drained by the provision of one 

 or two ditches to carry off the surplus water left after the main flood 

 waters have passed. A pond or swamp that is simply a basin in the 

 channel of a sluggish stream is more difficult to deal with, since the 

 water supply is continuous and fluctuating ; but it may be drained 

 by channelling the stream below the swamp to lower the water and 

 increase the flow, or it may perhaps be more effectively dealt with by 

 a combination of clearing and oiling. Swamps formed by seepage 

 outcrops can be dealt with only by aiming at the water table below 

 the surface. The only way of collecting such water issuing along a 

 hillside is bv means of ditches duo; at right angles to the flow of the 



