Perhaps our most effective agency in dealing with adult mosquitoes depends on the intense objection all species of these insects entertain to smoke. That it is quite possible to effectually protect animals from mosquito bites by the agency of smoke alone, has recently been conclusively shown in the course of Mr. Power’s experiments on the prevention of horse sickness in South Africa; but, though most semi-civilised people seem to live comfortably enough in a smoky atmosphere, Europeans would find such a state of things intolerable; and the plan can only be utilised to drive mosquitoes out of houses, other methods being relied on to prevent their re-entering. Smoke from almost any source will put mosquitoes to flight, and if sufficiently intense will stupefy them; but certain special materials must be burnt if it is desired to kill them outright, and our _modus operandi_ must be varied according to the means at our disposal, for if we can only expect to annoy the insects sufficiently to drive them out of doors, the latter must be left open during the fumigation; whereas, if it is proposed to kill them, all openings must be closed as completely as possible, so that the fumes may reach the insects in as concentrated a form as possible. For simply driving out mosquitoes, any fuel that produces a dense smoke, such as damp straw, will serve. Maize cobs are excellent for the purpose, but probably the least objectionable is the burning of a little incense (Hindustani, _Lobán_). To actually kill them, on the other hand, it is necessary to shut up all openings as closely as possible, and to burn certain special substances, such as sulphur, unopened chrysanthemum flowers, the leaves of the neem tree, tobacco, &c., and the degree of success attained will vary a good deal according to the character of the building in which it is attempted; it being obviously extremely difficult to secure an adequate concentration of the fumes in a very pervious structure, like a house with a thatched roof and walls of bamboo matting, such as is often met with in Burmah and the Malay Archipelago. Under such circumstances, the rapid burning of a large amount of the fumigating agent is the only way of meeting the difficulty; and under any conditions, plain sulphur, simply ignited as a powdered mass, or placed on the hot coals of a charcoal brazier, burns so slowly as to be quite useless.