THE MOSQUITO 87 



surface-film of the water, and help to maintain 

 the animal in a horizontal position just below 

 that film. When the larva relaxes its hold and 

 sinks into the water, it not infrequently 

 carries with it air-bubbles enclosed by these 

 fourteen ' fingers.' 



The eighth abdominal segment bears the 

 stigmata or the openings of the respiratory 

 apparatus, and the ninth segment has aban- 

 doned the flattened and square cross-section 

 of its predecessors, and is cylindrical and 

 tapering. The posterior end of the body is 

 cut off sharply. Round the posterior opening 

 of the alimentary canal are four white, soft 

 papillae, which are well supplied with tracheae 

 and are capable of contracting and expanding. 

 Above these are foiu' very prominent hairs, 

 two median and two lateral, and ventrally 

 to the ninth abdominal segment is a fan- 

 shaped arrangement of hairs springing from 

 two pieces of very complicated structures. 

 These hairs seem to act to some extent as 

 a rudder, and they probably serve as an 

 accessory organ of locomotion. Possibly they 

 have also a sensory or tactile function, and 

 act, as so many posterior filaments do in 

 insects, as antennae ' from behind.' 



We have referred above to the respiratory 

 openings, and, indeed, these are the key to 

 the whole situation. Close these openings — 



