AND SEEN FROM ABOVE.

From a photograph by Dr. C. W. Daniels.

used for collecting them. Anopheles bite chiefly in the darkness, and carry both malaria and elephantiasis; but A. rossii of India is negative as regards malaria.

One of the most important points about this kind of mosquito is that its larvae breed mostly in pools of water on the ground, and seldom in vessels of water. They do not, however, frequent all pools, but mostly those which are not so large as to contain minnows, nor so small as to dry up within a week or so, and which are not liable to scouring out during heavy rain. Such pools abound in flat, marshy country, in valleys, on the margin of lakes and rivers, in forests, on badlydrained roads, and in unkempt back yards; and it is for this reason that these places are often so malarious. The larvae are also found in the rushes at the margins of ponds and even rivers, in small weedy streams and ditches, in old wells and borrow-pits, in hollows in rocks filled with rain, in pits and pools by the side of railway and road embankments, in pools in drying watercourses, and sometimes in tubs and the bilge-water lying in boats and canoes. In marshes, they exist rather in the small pools at the margin than in the open flats of

water.

Anopheles abound in forest, bush, and open country covered with scrub-in all of which they feed on villagers, animals, and birds, and attack travellers in camps or rest-houses. A small proportion are found to contain the germs of malaria even away in the open country. But in and near the houses of natives, whose children so frequently contain the germs, a very large percentage of Anopheles are often infected; so that a traveller sleeping in or near native villages always runs a grave risk.

As already mentioned, Anopheles do not hum and

hover round their victims as much as other kinds of gnats do; and, as they often enter houses only at night, they are apt to be so little perceived that, even where they are most numerous, people will go away saying there are no mosquitoes in the place at all.

X. How To GET RID OF MOSQUITOES

We can protect ourselves from mosquitoes by mosquito nets and wire gauze screens to the windows, as described in sections XII and XVI. Many culicifuges, that is, substances to be rubbed on the skin for the purpose of driving away the insects, have been vaunted, but none of these have yet proved entirely reliable. In many cases we can certainly obtain much relief by getting rid of the insects themselves.

A good plan is to order a native servant to go round the house early every morning and kill every mosquito he sees. The insects can be killed on the wall by means of a fly-flapper, or caught in a small butterfly net and then crushed. If there has been any fever recently in a house this should always be done.

Another way to kill the adults in a house is to shut up all the windows and doors and burn some 'culicicide' inside. Sulphur lighted in a brazier or small flower pot or galley pot, put standing in a basin of water, is perhaps the best substance. Horticulturists use many patent chemicals in this manner for destroying 'green fly' and other pests in conservatories. I have heard that coarse, damp brown paper placed in a large tin and mixed with a little tobacco and burned, is very effective. One of the best culicicides is pyrethrum powder, bought from the druggist, damped and made into a small cone,

and then dried and lighted at the top (Howard). The smoke kills the insects-as most kinds of smoke appear to do. Gorgas extirpated yellow fever from Havana, in 1901, by destroying all mosquitoes with pyrethrum in infected houses and the neighbouring ones.

As a rule, however, instead of destroying the winged insects, it is easier to attack the helpless larvae living in water; or, still better, to do away entirely with the stagnant water in which only they can breed.

The simplest way to kill the larvae is to throw them out of the vessel, with the water in which they live, upon the dry ground; or, when they are in puddles, to brush them out with a broom. The ground absorbs the water and the larvae quickly perish.

If, however, the insects are found in water which is required for domestic purposes and cannot be wasted, as in cisterns and tanks, or in water which cannot be emptied out, as in wells and large pools, another method must be adopted. This consists in pouring a little thin oil on the surface of the water. The oil forms almost immediately a fine film over the whole surface and prevents the larvae breathing.

Ordinarily paraffin oil or kerosene is most commonly used; but crude petroleum and the cheapest and coarsest oils in the local market often do better. I advise the reader to make some experiments for himself with the cheapest oils he can procure. He should see that enough oil is used actually to kill the insects, and should, of course, use an oil which forms a film and which does not merely produce one or two globules in the water. For pools of water it is advisable to jerk the oil upon the surface, or to 'paint' it on with a rag tied to a stick. Oil has long been used on a large scale for this purpose in the United States, and is being employed in Havana and Sierra Leone.