THK CANADIAN KNTOMOLOGIST 39 



between the Muscid-Masiceralid stocks on llic one hand and the 

 Megaprosopid-Cnterebrid stocks on tlie (Ahcr. We retnrn al this 

 point to an approximation of the gronp concepts of Schiner, who 

 had an excellent eye for main natural distinctions in the Diptera. 



The Megaprosopid type is clearly, though ncjt closely, allied 

 with the Dexiid, but its facial plate structure is closer to the Oestrid 

 type than to the Dexiid, while the uterus and first-stage maggot 

 as well as the cephalopharyngeal skeleton of latter differ markedly 

 from those of the Dexiidae; hence it is advisable to maintain the 

 group separately for the sake of uniformity. 'Inhere has been a 

 differentiation of the facial plaic in the Sarcophai^idae; the I'ara- 

 macronychiine, Miltogrammine and Macronychiine types ex- 

 hibiting a successive specialization in the direction of the Dexiid 

 and Megaprosopid-Oestrid types. This is a case in whicii the 

 facial jilate characters are subordinated to the reproductive. It 

 must be noted that the family group Dexiidae as restored does not 

 include the many forms of the l^seudodexiine and Pyrrhosiine 

 types, all oi which have the I'Lxoristid facial plate, though many 

 of them possess pubescent and even densely plumose arista. 



There are two large and taxonomically very i)racticable 

 groups heretofore left in the Exorislidae that may most advantage- 

 ously be accorded family rank at the [present time. These are the 

 micrf)type-egg forms with leaf-oviposition habit so far as known, 

 which constitute the Masiccratidae; and the minute-platelet, col- 

 oured-maggot forms with f(;liage-larviposition habit so far as known, 

 which constitute the Ilystriciidae. There are three main categories 

 of the former differing in the shape of the maggots and eggs; be- 

 sides whicli there are ninnerous types differing in the structure of 

 the chorion, which (piite certainly indicates intu li diversity of 

 origin. Yet they form a gnmp easily defined on dissection of the 

 females, and taxonomically cjuite as tenable as the Oeslridae and 

 several other long-accepted families. 



The group of which Phasiupleryx is the type merits family 

 rank on the remarkable and, so far as yet known, unicpie change 

 of the eggs in the uterus from microtype ovate to macroty[)e sub- 

 cylindrical, indicating wide separation from other stocks; not to 

 mention the very exceptional structure of the first-stage maggot, 

 which is no doubt largely adaptive. 



