BRITISH BLOODSUCKERS 251 



hand by clenching your fist hard, you will find 

 that she cannot any longer withdraw her man- 

 dibles ; they are caught fast in your flesh by their 

 own harpoon-like teeth, and there she must stop 

 accordingly till you choose to release her. If you 

 then kill her in the usual manner, by a smart slap 

 of the hand, you will see that she is literally full of 

 blood, having sucked a good drop of it. 



The humming sound itself by which the mos- 

 quito announces her approaching visit is produced 

 in two distinct manners. The deeper notes which 

 go to make up her droning song are due to the 

 rapid vibration of the female insect's wings as she 

 flies ; and these vibrations are found by means of 

 a siren (an instrument which measures the fre- 

 quency of the waves in notes) to amount to about 

 3000 in a minute. The mosquito's wings must, 

 therefore, move with this extraordinary rapidity, 

 which sufficiently accounts for the difficulty we 

 have in catching one. But the higher and shriller 

 notes of the complex melody are due to special 

 stridulating organs situated like little drums on the 

 openings of the air-tubes ; for the adult mosquito 

 breathes no longer by one or two air-entrances on 

 the tail or back, like the larva, but by a number of 

 spiracles, as they are called, arranged in rows along 

 the sides of the body, and communicating with the 

 network of internal: air-chambers. The curious 

 mosquito music 'thus generated by the little drums 

 serves almost beyond a doubt as a means of attract- 

 ing male mosquitoes, for it is known that the long 

 hairs on the antennae of the males, shown in No. 9, 



