OF WASHINGTON, VOLUME XIII, 1911. 41 



into the mouth-cavity, does the lower face finally harden and take on 

 color and form . 



If one compares pupae of Muscidae and Syrphidse in an equally ad- 

 vanced state of development the difference is also very obvious, for in 

 the former the head is conically inflated between the base of the an- 

 tennae and the vertex, which inflation represents the frontal bladder, 

 while in the latter these parts already have the position which per- 

 tains to them in the emerged insect 1 . 



Thus it is seen that the Aschiza, in their mechanism for 

 escaping from the puparitim as in other respects, represent a 

 less specialized type than do the Schizophora with their 

 highly developed and persistent frontal bladder. This is sup- 

 ported by the fact, brought out in the anatomical investiga- 

 tions of Dufour, 2 that, as one follows tue evolutional lines, 

 there is a reduction in the size of the food-reservoir until 

 finally, in the Hippoboscida?, it is lost altogether; accompany- 

 ing this there is a lengthening of the digestive tract itself. 

 Dufour touches this point in discussing the conditions in the 

 Hippoboscidse. 



The alimentary tube in them is the longest of all the Diptera, since 

 it is from eight to nine times the length of the insect. That of the 

 last genera of the acalypterates has already prepared us for the pro- 

 gressive increase in the length of this canal, together with a progress- 

 ive reduction in its organization. 3 



A consideration of these conditions in the Phoridae seems to 

 throw some light on the position of the family, for after con- 

 siderable discussion this seems to be still unsettled. The adult 

 characters give opportunity for wide divergence of opinion 

 and apparently present nothing that is decisive. Becher, as 

 already stated, placed the Phoridae in the Aschiza, in spite of 

 the fact that there is no trace of a frontal lunule, and in this 

 he is followed by the majority of dipterists. Osten Sacken, 

 on the other hand, has shown that, if the larval and pupal con- 

 ditions are properly understood, the family should be grouped 

 in the Orthorrhapha, and a few authors have followed him. 4 

 Brues, in his Monograph of the North American Phoridae 5 and 

 in more recent papers, considers the systematic position of the 



1 L. c., pp. 51-52. 



2 Recherches anatomiques et physiologiques sur les dipteres. Mem. 

 Acad. Sci., vol. 11, pp. 171-360, pis. 1-11 (1851). 



3 L. c., p. 341. 



4 The position of Phora in the system of Diptera. Ent. Mo. Mag., 

 vol. 38, pp. 204-205 (1902). 



5 Trans. Amer. Ent. Soc., vol. 29, pp. 331-404, pis. 5-9 (1903). 



