OF WASHINGTON, VOLUME XIII, 1911. 37 



the body fluids. The important part played by the abdominal 

 and thoracic muscles in this process has been repeatedly 

 pointed out, but no one seems to have suspected that air, 

 ingested at this time, acts as an auxiliary. I have opened a 

 newly emerged flesh-fly (Calliphora) and found that the 

 paunch or food reservoir was filled with air. But it appears 

 that in the Cyclorrhapha the presence of air plays but a very 

 subordinate part in effecting the escape of the imago from 

 the puparium; indeed, it is to be doubted if in those forms in 

 which the food-reservoir is lacking (Hippoboscidae) air is em- 

 ployed at all. 



The process of emergence in the Cyclorrhapha is very fully 

 described by Kiinckel d'Herculais in his great work on the 

 Volucellas. 1 He points out that the action of the frontal 

 bladder has been observed bv Reaumur in Calliphora vomi- 

 toria; -by Von Gleichen in Musca domestica, figuring the head 

 in two different phases of the process; by Reissig in the 

 Tachinidae; by Weissman and by Lowne in several Muscidae; 

 and by himself in the Syrphidae (VolnccUa, Eristulis, Svr- 

 p/ius] and the higher flies (Anthomyia, Pegomyia, Calli- 

 phora, Litcilia). To these must be added the observations of 

 Joly on the emergence of the Oestridae. 



Kiinckel d'Herculais brings out the fact that, while the 

 frontal bladder is present in all the Cyclorrhapha at the time 

 of emergence, there are important differences between the 

 lower forms, such as the Syrphidae, and the higher or mus- 

 coidean forms. Upon these differences, although he under- 

 stood them but imperfectly, Becher founded his two groups, 

 the Aschiza and the Schizophora, groups which appear to 

 be well founded, both on biological and structural char- 

 acters. 2 The difference in the two groups consists in the 

 disappearance of the frontal bladder with the hardening of the 

 integument in the first group, while in the second the bladder 

 persists in a retracted condition. Consequently a frontal su- 

 ture is present in the Schizophora and absent in the Aschiza. 



Kiinckel d'Herculais describes the emergence of Volnrclla 

 as follows: 



Carefully enclosed in its nymphal envelope the fly is incapable of the 

 least movement; its legs, its wings, the mouth-parts, the antennae, 

 are folded down upon the inferior region of the body in such a manner 

 that the front protrudes as the most prominent part. If one opens a 



'Recherches sur 1'organisation et le developpement des Volucelles, 

 Paris, 1875, (atlas) 1881. 



2 Zur Kenntniss der Kopfbildung der Dipteren. Wiener entom. Zei- 

 tung, vol. 1, pp. 49-54 (1882). 



