THE MOSQUITO 89 



the outer air through these breathing - pores. 

 From time to time the hairs mentioned above 

 are brushed over by the mouth parts and 

 cleaned of any debris. 



The larvae, when they leave the surface- 

 film sink by their own weight; but they not 

 infrequently swim actively downwards, their 

 swimming action being very like that of an 

 eel. When returning to the surface they are 

 entirely dependent upon their powers of 

 swimming, being slightly heavier than water. 

 When the tail reaches the surface-film the 

 larvae are at once arrested, and immediately 

 cease their swimming-movements. They in- 

 variably move tail forwards, and the hairs 

 which we have mentioned above at the posterior 

 end of the body undoubtedly act as ' buffers ' 

 or ' fenders.' As a rule, when they are above, 

 they are actively engaged in feeding; but at 

 the bottom they lay inert, as though feigning 

 to be dead. Kept in a glass beaker they are 

 apt to lie with their respiratory apparatus 

 attached to the concave film, which capillary 

 attraction draws up on the surface of the 

 glass. Their heads then point towards the 

 surface of the beaker. If forcibly kept below — 

 say, by submerging them under a watch-glass 

 — ^they are frequently enabled to breathe by 

 attaching the openings of their respiratory 

 apparatus to an air-bubble. 



