VI MOSQUITO CONTROL 249 



mosquitos should so far as possible be abolished. Care should be taken 

 not to allow old tins or other vessels to lie about on the ground. Pools 

 should be drained and permanent springs where water oozes out should 

 be covered with gravel or cinders. 



Accumulations of water which cannot be abolished should be rendered 

 inhospitable to the mosquito larvae. Large pools round lakes should be 

 opened up so as to allow free access, of insect-eating fish. Open ditches 

 should be kept free from water-weeds which afford shelter to the larvae. 

 Water butts should be covered in with sacking or wire gauze, an overflow 

 being provided some inches lower down to ensure that the water level 

 shall not rise up to the screen and so become accessible to the egg-laying 

 mosquitos. 



In cold temperate climates the malaria problem is less insistent, the 

 long cold season allowing the majority of malarial patients to recover 

 sufficiently to be no longer infective to mosquitos that bite them. In 

 Britain Malaria or " Ague " is in normal times of little importance but 

 at particular periods, especially after great wars, epidemics are liable to 

 be started by the arrival in the country of large numbers of persons 

 infected with the parasite who serve in turn to infect the local anopheline 

 mosquitos. Of these there are three species of Anopheles — A. maculi- 

 pennis, A. hifurcatus and A. plumbeus. 



A . macuUpennis is the most important species of the three, as it is 

 common and frequents the neighbourhood of houses. It begins to 

 deposit its eggs in the spring in weed-grown ditches and ponds in the 

 neighbourhood of houses. A point to be noted is that this species is 

 normally tided over the winter season not, as is usual, in the larval 

 condition but in the adult stage — fertilized females hibernating in warm 

 cowsheds, stables or other outhouses where they may readily be found 

 hanging on to the roof. These hibernating females are not entirely 

 inactive for they take advantage of occasional warm sunny days to get 

 a meal of blood. It is obvious from what has been said that the numbers 

 of A . macuUpennis in such a cold temperate climate as that of Britain are 

 controllable (i) by the destruction of the hibernating females by fumi- 

 gation or whitewashing and (2) by removing the vegetation from ditches 

 and ponds near houses. 



A. hifurcatus, whose larvae frequent the mud at the bottom of ditches 

 and winter in that condition, and A. plumbeus, whose larvae have 

 been found usually in holes in trees, are more elusive as regards con- 

 trol measures but they are of much less practical importance than 

 A. macuUpennis. 



No special attention has been drawn so far to the obvious advisability 



