THE MOSQUITO 47 



deeper into the integument the body of the 

 mosquito approaches nearer and nearer to the 

 skin of the victim, and the labium is pressed 

 farther and farther backwards until at the end of 

 a satisfactory puncture the distal and proximal 

 parts of the labium are parallel and touching. 



It is rather an interesting point that the 

 labium does not enter the skin, because the 

 larvae of certain Filarias — one of which pro- 

 duces elephantiasis in man, and the other 

 severe heart trouble in the dog — are found in 

 pairs — probably a male and a female — in the 

 labia of mosquitos. How exactly these nema- 

 tode larvae leave the labium of the mosquito, 

 and enter the body of the man and the dog, 

 has not definitely, I believe, been cleared up ; 

 but that they do enter the human and the 

 canine skin seems certain. 



We have mentioned that the labrum is a 

 grooved tube with its edges practically in 

 proximity, and it is up this tube that the blood 

 of the bitten is sucked by the well-known 

 suctorial pharynx which occupies so large a 

 part of the interior of the head of a mosquito. 

 Much the most dangerous weapon of the whole 

 armoury, however, is the hypopharynx. This 

 is shaped like a double-edged sword with a 

 very minute groove running down the centre ; 

 this groove is so minute that Professor Nuttall 

 and I and others for some time took it to be a 



