22 



DIPTERA — PUPA 



[CH. 



larva casts off its skin before pupating. This type of pupa 

 is found, with few exceptions, throughout the members of the 

 Brachycera and Nematocera. In the coarctate forms there are 

 no external protuberances, with the possible exception of a 

 pair of projections at one end of the body, but the whole 

 pupa looks like a tiny barrel, with rounded ends. In this 

 case the pupating larva does not escape from its skin at the 

 last moult but merely shrinks within it, and the larval skin 



Fig. 9. 



Fig. 8. 

 Fig. 8. Obtectate pupa of ^ BO^Ae/es maculipennis. iy, respiratory trumpet. 



After Nuttall and Shipley. 

 Fig. 9. Coarctate pupa of Stomoxys calcitrans. After Newstead. 



is strengthened by the secretion of chitin so that it forms an 

 adequate protection for the pupa. The external case is fre- 

 quently known as the puparium. This type of pupa is found 

 in the Cyclorrhapha, which includes the house-fly, Stomoxys, 

 Glossina, etc. 



The adult fly escapes from the pupal case in one of two 

 ways. In the obtectate forms the dorsal surface of the pupal 

 sheath splits longitudinally or in a T-shaped fashion, and the 

 insect draws itself out through the opening. In the coarctate 

 pupffi the anterior end of the pupal case is pushed off by means 

 of the expanded ptilinum of the emerging fly {vide supra, p. 14). 



