52 C, HERBERT HURST. 



protrudes, and the head, then the abdomen, and lastly the wings, 

 legs, and proboscis are drawn out of the pupal cuticle, which is left 

 floating in the water while the imago flies away. 



"With the cuticle are cast off nine pairs of fragments of tracheal 

 intima, two pairs being drawn out through the thoracic stigmata, 

 the others through the stigmata of the first seven segments of the 

 abdomen. 



These fragments differ as follows. The first pair are well developed, 

 and have the spiral thickenings very well marked. They are con- 

 tinuous with the lining of the respiratory siphons, and formed 

 during pupal life the connection between these organs and the 

 tracheal system generally. 



The first abdominal pair are not so well developed, but the spiral 

 thickening is recognisable in them, and the terminal portion of each 

 is better developed than the rest, and is beset internally with 

 numerous small spines. It was through these that the tracheal 

 system communicated during pupal life with the air-cavity beneath 

 the thorax. The remaining fragments, i.e., the hinder thoracic pair, 

 '•and all the abdominal pairs except the first, are very thin and 

 delicate, and were functionless during pupal life. 



The cuticular lining of the anterior and posterior portions of the 

 alimentary canal and the cuticle of the invaginated larval siphon are 

 also shed, together with all setse and the whole of the pupal siphons 

 and fins. These three last alone involve the loss of portions of 

 tissues other than cuticle. 



The imago, with its long, slender body, wings, legs, and proboscis, 

 hardly needs to be described. Like pupa and larva it breathes air, 

 but now by more numerous stigmata, and unlike them it flies in the 

 air. The larva fed upon solids ; the pupa did not eat at all. The 

 imago feeds upon fluids, and the female, at least, upon the hot blood 

 of man and other mammals. The male is short-lived, and his food 

 is said to consist of the sweet juices of flowers. To find the female 

 and to impregnate her are the real objects of his short life. His 

 antennge are provided with long hairs, which A. M. Mayer (3) has 

 shown to be sensitive to a particular sound when the head is turned 

 towards the source from which it proceeds, and he has further 

 shown that sound to correspond to the note emitted by the vocal 

 organs which Landois (4) has described on the sides of the thorax 



