428 LT.-COL. S. p. JAMES. 



importance of permanent and temporary breeding-places has been worked out in 

 detail. The account on pages 82-83 of Major Christophers' report on " Malaria in 

 the Punjab "* shows clearly, I think, that what Mr. MacGregor has described as 

 happening in his area this year is what happens each year in certain large tracts of 

 that country. With respect to the various mosquitos which are indigenous in an 

 area, Major Christophers pointed out that, however hard pressed by drought some 

 of them may be in a particular part of the area, it is always possible to find, within 

 their usual distance of spread, some permanent collections of water in which they 

 are breeding freely. Also, that when temporary breeding-places reappear, the 

 various species spread widely from these permanent sources (which he calls 

 " mosquito sanctuaries ") until in a short time they can be found again throughout 

 the area. This explains the well-established Indian observation that a particularly 

 dry year has no permanent effect in reducing Anopheles mosquitos. In the 

 Punjab the chief Anopheles " sanctuaries " were found to be : — (1) Large river-beds 

 like those of the Jumna, Beas, etc. ; (2) jheels and large tanks filled with aquatic 

 vegetation, with their associated swamps and pools ; (3) extensive brickfields and 

 large excavated pits near towns and villages ; (4) irrigation systems. 



Nearly the same headings would be applicable to the permanent mosquito 

 " sanctuaries " in Surrey and Kent. As some of them exist within a few miles of 

 the area reported on by Mr. MacGregor, a probable answer, based on Indian 

 experience, can alread}' be given to his question whether the species dealt with will 

 be rare in his locality during future years. 



* Scientific Memoirs by Medical Officers of the Government of India, New Series No. 46, 1911. 



