48 THE CANADIAN ENTOMOLOGIST 



larger type, as we must needs conclude they have done, in sufficient 

 mode to become established, necessitating corresponding marked 

 changes in the oviposition habits and thus in the instincts of the 

 female, is a fascinating problem for solution. It seems certain, 

 moreover, that such eggs have arisen independently in several 

 different stocks, but probably largely through parallelism due to 

 evolution trend. 



The flies with subcutaneous host-larviposition habits and 

 those with subcutaneous host-oviposition habits are likewise 

 much specialized. The remarkably specialized piercers, larvi- 

 positors, ovipositors, combinations of these, and accessory struc- 

 tures such as the ventral carina and its spinules denote high speciali- 

 zation. During copulation the piercing structures have evidently 

 to be extended or thrown far backward, in the Compsilurice at least, 

 for effecting the union of the vaginal orifice with the male. 



While Phasiopteryx appears to be a waning survivor of an old 

 stock with dexiid affinities, it exhibits a large amount of speciali- 

 zation in its very long and slender uterus and especially in its very 

 differentiated isopodiform maggot with chitinized segmental lateral 

 and dorsal plates. But what holds the utmost attention and 

 interest in this form is the wholly unique character of the ova 

 accomplishing in the upper part of the uterus their final growth 

 or increase in size to the fully formed macrotype egg, which should 

 by analogy with other macrotype-egg forms have been com.pleted 

 in the ovarioles. This seems difficult of explanation and, of course, 

 at once suggests some connection with the microtype-egg or leaf- 

 ovipositing forms. But Phasiopteryx is to all appearances of external 

 structure far removed from the microtype-egg stocks. Its uterus 

 is very similar in general form to that of the Phasiatactice and Cne- 

 phalomyiia;, both of which have an elongate and more or less 

 pointed microtype egg that is flattened ventrally. Its facial plate 

 is not so divergent in type as to preclude a common origin with 

 the masiceratid stocks. It seems probable that we must look on 

 Phasiopteryx as a remnant of an offshoot from some ancient mi- 

 crotype-egg stock. If this view is correct, we may expect important 

 light on phylogeny of the microtype-egg stocks from a 

 thorough study of this genus and its allies. It appears quite 



