86 MOSQUITOES 



almost entirely clear and larv* congreg:atecl over this sediment, 

 feeding head down and frequently rooting into it; varying the 

 process by working along the glass of the jar on the side away 

 from the light. It was very rare that an individual was 

 observed at the surface with the spiracle in breathing position. 

 I watched patiently several times, for fifteen minutes at a time, 

 without noting a single individual rising to the top. Mr. Dick- 

 erson, one of the students, watched more or less continuously 

 for two hours on one day and declares positively that during 

 that period only a small percentage of the entire number came 

 to the top. On two or three occasions where my work was such 

 as to allow it, I kept a jar within sight the entire day, and I 

 have no hesitation in saying that some individuals remained 

 below the surface for hours. 



Occasionally a number of specimens would be at the surface, 

 feeding, head up, so that the mouth-brushes skimmed the sur- 

 face, and these w^ere watched on occasions for fully twenty 

 minutes without noting any attempt to assume the breathing 

 position. In fact, during the two months that these larvfe were 

 under daily observation, the rising to the surface to breathe was 

 the rare exception rather than the rule. 



As to feeding positions, all of those figured by Dr. Howard 

 were noted. Usually they were head down, over the bottom 

 sediment, or head up, feeding along the sides of the glass or at 

 the top. The mouth-brushes serve as organs of locomotion as 

 well as for feeding, and the insects are perfectly able to make 

 their way from place to place Avithout moving any other part of 

 the body. 



The jerky, wriggling motion is used w^hen they wish to get 

 away quickly, and as often to get down to the bottom as to get 

 up to the surface. They can, and often do, sink slowly to the 

 bottom without any motion Avhatever, and often, to sink more 

 rapidly, they curl themselves up into a ring. Occasionally a speci- 



