BACOT : MOSQUITOES AND THE DANGER OF MALARIA. 259 
readiness or movement of its hind legs. Larvae and pupae 
of mosquitoes are devoured by fish, newts, water-beetles and 
their larvae, by dragon-fly larvae, by various species of water-bugs, 
and by the larvae of some species of ephemerids. There are, 
further, the cannibal larvae of their near relatives and allied 
groups, which are by no means the least dangerous of their 
foes. Competitors for the food they need while in the larval 
stage also check the increase of the mosquitoes. In some instances, 
these competitors are so numerous and so efficient as to starve 
the larvae ; in other cases, they increase their danger from other 
enemies by prolonging the larval period. Tadpoles and water- 
snails in the larger ponds devour the raw material from which 
their food would be developed. .Small Crustacea and the larvae 
of Chironomus are so efficient as scavengers in small collections 
of water that they may actually starve the mosquito larvae. 
VI. —Methods for the Combating of Mosquitoes by Man. 
The inventions of man for combating mosquitoes may be 
summarised as follows :—The use of mosquito curtains ; the 
screening of dwellings ; the use of preparations to prevent the 
insects biting ; the destruction of adults by traps, fumigation, 
or spraying ; the removal of cover near houses ; and the cutting 
of trees, bushes, and grass. Further, mosquitoes are open to 
attack in the larval and pupal stages by the drainage of surface- 
water and swamps, the filling of pools and water-holes, the 
removal of weeds in streams and ponds, the deepening of the 
margins of ponds, the filling of hoof-holes, the oiling of water- 
surfaces, and the penalising of persons who allow mosquitoes to 
breed in lily-ponds, rock-gardens, swamps, water-tanks, water- 
butts, and other domestic supplies of water, and those who leave 
about discarded tins and empty bottles. 
Before deciding upon the most suitable methods of control 
for any district, careful consideration must be given to their 
effect on, or interaction with, any of the natural enemies of the 
mosquito. If this is not done, more harm than good may re¬ 
sult. For instance, the filling of a pond may destroy a breeding 
place for their enemies (such as water-beetles, dragon-flies, 
newts, toads, frogs, etc.), with the result that the numbers of 
these may be reduced. The gain resulting from the removal of a 
breeding place in which relatively only a very few of the mosquito 
