218 THE ENTOMOLOGIST. 



*(7.) M. tristis, Ckll., one male, at flowers of Ipomoea mexicana. 



*(8.) Anthophora vallarum, Ckll., one male, two females, at 

 flowers of Ipomoea mexicana. 



(9.) Megachile occidentalis, Fox, one male, at flowers of Heli- 

 anthus annuus. 



(10.) Xylocopa arizonensis, Cress., one female, at flowers of 

 Ipomoea mexicana. Instead of entering the corolla, it cut a slit 

 on the outside, near the base. 



MOSQUITOS AND MALARIA. . 

 By Guy A. K. Marshall, F.Z.S. 



As the above subject hardly appears to have received the 

 attention it merits in British entomological journals, it was a 

 pleasure to read Mr. G. W. Kirkaldy's all too short resume of 

 the views of Celli and Grassi on the question in the ' Entomolo- 

 gist ' for April, 1900. The facts and contentions set forth in this 

 resume would seem to leave but little doubt that mosquitos of the 

 genus Anopheles are the sole carriers of malarial contagion, and 

 that they themselves can, in turn, only acquire the parasites 

 from malarial man. Yet the fact remains that in a malarious 

 country like Mashonaland, where probably three-fourths of the 

 inhabitants have had a practical experience of the disease, the 

 theory is regarded with a considerable amount of scepticism, not 

 merely by laymen, but also by the majority of medical men. 

 While personally I do not share this scepticism, I can yet appre- 

 ciate the difficulties which stand in the way of the acceptance of 

 the theory in its present form, when tested by experience in a 

 malarial country ; and therefore it may be useful to draw atten- 

 tion to these counter-arguments, in the hope that they may be 

 satisfactorily explained away. 



If we accept the proposition that malaria can only exist in 

 the presence of two factors, viz. malarial man and Anopheles, 

 then we are logically bound to accept the conclusion that, if a 

 man, or party of men, free from malarial poison, should pene- 

 trate from a healthy area into an unhealthy, but uninhabited, 

 region, it would be impossible for them to contract fever, how- 

 ever much they might be bitten by mosquitos ; further, it follows 

 that all uninhabited regions, even of comparatively small size 

 (seeing that the range of individual specimens of Anopheles is 

 apparently very limited in extent), must be entirely devoid of 

 malaria, even though they may be full of swamps, and teem with 

 mosquitos. 



Such conclusions certainly do not appear to be borne out by 

 experience. It would doubtless be difficult to find many areas in 



