THE CANADIAN ENTOMOLOGIST 37 



INQUIRY INTO THE RELATIONSHIPS AND TAXONOMY 

 OF THE MUSCOID FLIES. 



B\ C. H. T. TOWNSEND, LIMA, PERU. 



Dissections of the female reproductive system and studies of 

 the eggs, first-stage maggots and reproductive habits of these 

 flies, carried on for the past five years, have proved a golden key 

 for unlocking many of the secrets connected with their relation- 

 ships. Throughout the work, however, the problem of harmonizing 

 these characters with those of the external adult anatomy has 

 been a diflficult one. At first sight the results seemed to indicate 

 that the family groups heretofore recognized do not exist in the 

 commonly accepted sense. The ordinary divisions seemed almost 

 untenable, being often at variance with the results of the dissec- 

 tions or with external adult characters of well known utility. 



It was soon evident that no satisfactory classification could be 

 built up on the reproductive system characters alone. As examples 

 of the disagreement between reproductive and external adult 

 characters, the Phasiidae show in part flat-ovate macrotype eggs 

 without uterus, in part elongate eggs deposited subcutaneously, 

 also without uterus; and, if the Rutiliine and related flies are in- 

 cluded in the family, in part elongate subcylindrical eggs hatching 

 in an elongate uterus. The Exoristidae, after being restricted 

 greatly from their former limits, are still more markedly difTer- 

 entigited in type of reproductive system and egg, showing not only 

 the three Phasiid types but a half dozen or more additional ones 

 as w'ell. 



It is now quite apparent that the external adult characters 

 can not be subordinated to the reproductive characters in quite 

 a good many cases, though they can so be in other cases. It seems 

 practically certain, for example, that parallel specializations of 

 the reproductive system have arisen quite independently in these 

 flies, and that marked and parallel difi^erentiations of the facial 

 plate have so arisen with far less frequency. Facial plate dififeren- 

 tiation is largely dependent on a greater or less lapse of oral and 

 antennal functions, and such lapse is not of frequent occurrence. 

 Reproductive system and egg modifications manifestly play an 

 extensive part in the econ"omies of these flies, wherefrom we may 

 conclude that the reproducti\'e system is plastic in a greater degree 



February, 1913 



