REPORT OF THE MALARIA EXPEDITION. 
31 
(7.) Etnhanktufnti favour malar'ui.— They also favour the formation of surface puddles. 
(8.) Towns art' inimical to malaria. — Stagnant surface puddles are not likely to be as 
numerous in crowded, well-drained cities, as in rural areas. 
(9.) Cultivation and surface drainage tend to remove malaria. — They also tend to remove 
waste water suitable for Anopheles and lying on the ground. 
(10.) Malaria is not particularly connected with large hodies of ivater. — Gnats do not often 
breed in such. 
(11.) Malaria occurs on ships.- Gnats, including Anopheles., visit ships. 
(12.) // is particularly dangerous to sleep in malarious places, especially at night. — Gnats easil)' 
bite sleeping persons, and usually feed at night. 
(13.) Ground floors are most dangerous. — Gnats seem to remain near the ground. 
(14.) Mosquito-nets protect from malaria, — They protect also from gnats. 
(15.) Warmth favours malaria. — It favours also gnats, and the Haemamoebidae within them. 
In the remarkable work [i] which seems to be the first published exposition of the gnat- 
theory of malaria. King suggested many of these striking analogies — and indeed based his theory 
on them. Laveran, Manson, Bignami, and others have also independently entertained the same 
ideas — which may well occur to anyone who considers the subject at all. But it is now necessary 
to make an important correction in these views. King — and indeed other observers — seems to 
have thought that all gnats rise from swamps. A close student of the bionomics of gnats, 
however, might have almost shattered the whole argument at the outset by remarking that many 
of the commonest gnats do not rise from swamps at all, but from tubs, pots, etc., in the vicinity of 
houses ; and are indeed most prevalent in the heart of large cities and in other places where there 
is little or no malaria. It is clear, then, that King's arguments can apply only to certain species of 
Culicidae, namely, those which breed only in pools on the ground. 
King also employs other analogies which seem to be less sound. Accepting the popular 
views, he considers that both malaria and gnats can be blown long distances, as to the summits of 
hills. It is probable that in many such cases the gnats really breed close at hand ; though the 
observer, under the influence of the popular superstition, prefers to think that his malaria comes 
from the nearest marsh, although that marsh may be miles distant. King also suggests that white 
men are more susceptible than black men, because gnats can see the former more easily. As a 
matter of fact, it is always observed that gnats prefer to settle on dark surfaces ; while the 
susceptibility of white men is more probably due to comparative absence of immunity than to 
more frequent infection. 
22. Are other Insects besides Anopheles hospitable to the Human Haema- 
moebidae ? — Returning to the subject just touched upon, it will be readily perceived that out of 
the fifteen analogies given in the last paragraph, no less than nine (the first nine) can apply only 
to insects which breed in pools of water on the ground. For instance, they will not apply to 
species of gnats which usually breed in vessels of water. Such gnats cannot be said to have a 
localized distribution, because they are to be found in the neighbourhood of almost every dwelling 
