38 
REPORT OF THE MALARIA EXPEDITION. 
26. Precautions against the Bites of Gnats. — We sliall content ourselves with 
recording a few practical remarks in this connection. 
(i.) Numerous substances have been vaunted as being efficient culicifuges,'' such as oil 
of lavender, eucalyptus, kerosene oil, etc. [12]. It is scarcely advisable to trust to any of them 
until their value has been demonstrated by experiment. Even if an effective cuHcifuge exists, 
it is hardly to be expected that many persons in malarious localities will use it constantly. 
(2.) Lights in a bedroom tend to prevent gnats from biting — not by attracting them, as 
many suppose ; but more probably by alarming them. They seem to prefer darkness for feeding. 
Many species of gnats bite voraciously during the daytime, even in verandahs and under trees. 
These are generally gnats of the C. taniatus type. 
(3.) In India, natives certainly seem more prone to infection than Europeans. This 
may be partly attributed to their wearing less clothing and not generally sleeping in mosquito- 
nets. It should be observed, however, that natives of India (and, we believe, negroes) generally 
sleep with a sheet drawn over their heads, for the express purpose of keeping off gnats ; and the 
method is undoubtedly partially effective. 
(4.) Some writers imagine that the darkness of the skin of the coloured races is a preventive 
against gnats. As a matter of fact, it will be generally observed that gnats settle on dark surfaces, 
and are probably attracted by dark skins, instinct telling them that tliey are likely to find their 
food there. 
(5.) In India it is universally recognised that fans and punkahs keep away gnats to a large 
extent. Thus many persons dispense with nets and sleep only under punkahs — a questionable 
practice in the presence of Anopheles^ because, unless the punkah swings rapidly just over the 
body, gnats are not much deterred by it. 
(6.) Mosquito-nets must be entirely free from holes, because gnats find tiieir way through 
the smallest aperture. They sliould also have a doubling or valance just above the surface of the 
bed, in order to protect tlie hands, feet, and knees of tiie sleeper when tlirust against the net during 
sleep. If the weather is hot the net should not be dispensed with, but a punkah may be employed 
over it. The top of the net should be made of gauze. Tent-shaped nets are hot and close 
because they fall in folds. A rectangular net, tightly stretched inside a wooden framework, and 
carefully tucked under the mattress, is much better. The net should never be allowed to fall to 
the floor. Unless care is taken while getting into bed, gnats frequently enter with the occupant. 
Mosquito-nets are often used in so stupid a manner that, instead of excluding gnats, they include 
them — gnats whicli have previously entered being allowed to remain within the net for days. 
(7.) Screens to windows are little employed. They would probably be very effective 
indeed. They should be made of fine wire with a fairly large mesh, and should be fixed 
immovably if possible, because gnats find their way in and out of windows at all times of the day. 
Tliey are often employed in America. 
(8.) Some persons have such a dislike to being bitten that they are constantly on the watch 
for " mosquitoes," and drive them away or kill tliem whenever possible. Such certainly escape 
much more tlian those wlio are indifferent to the insects, or those wlio think they arc immune 
against tliem. 
