THE ANATOMY OF THE PUPA 67 



trumpets are protruded, the abdominal tracheae appear to 

 collapse, and the animal floats with the anterior end 

 upwards, the new syphons coming to the surface. The 

 soft parts of the old respiratory syphons are withdrawn from 

 the cuticle and invaginated into the eighth abdominal 

 segments while the lining of the tracheal trunks breaks up 

 into pieces, which in the abdomen correspond to the 

 segments, and is cast off, with the other larval exuviae, by 

 means of the mechanism that has been already described. 

 The pupa which thus escapes, differs greatly from the 

 larva. It is in the larger species a little under 1 cm. in 

 length when fully extended, and consists of a bulky, 

 laterally compressed mass, made up of the head and thorax 

 with their appendages, and of a slender flexible abdomen, 

 which when at rest is carried curled under the thorax. 



In a specimen 9 mm. long the thorax was '2"5 mm. and 

 the abdomen 6 '5 mm., but the thorax appears much longer 

 on account of the wings, which extend downwards and 

 backwards from its sides. The head adds nothing to the 

 length, as it is carried tucked down under the thorax. It 

 is broad from side to side, short from back to front, while 

 ventrally it is drawn out into a long process, which extends 

 backwards under the thorax as far as the anterior part of 

 the abdomen, where it curves upwards. This process is 

 made up of the mouth parts, and includes all the parts 

 represented alike in the adult and larva. 



On throwing off their larval chitinous covering, the 

 parts retain their larval masticatory type, but during the 

 four days of pupal existence the various parts mould them- 

 selves and develop into the basis of the adult condition, so 

 that by the time the chitin of the adult is ready for indura- 

 tion, they have altered their form to that of the adult 

 mouth. From the sides of the epicranial region, the 

 antennae run outwards to the sides of the thorax, one 

 beneath the anterior margin of each wing. The head and 

 all its appendages are immovable during the pupal stage. 



The thorax is rounded, but somewhat compressed from 

 side to side. From the sides of its summit arise the respira- 

 tory syphons, a pair of conspicuous organs whose position 



