ARRANGEMENT 49 



but the association of two such sharply marked characters facilitates their 

 study. The remaining Tkomoptera {Boinbylidce and Thcrcvidce) and all 

 the remaining Beachycera may then be distinguished by their possessing 

 only two pad-hke pulvilli, with the empodium either absent or reduced to 

 a simple bristle ; so that there can be no confusion with the Eremoch^ta 

 even in those cases where bristles are replaced by dense or coarse 

 pubescence. 



Other details given by Osten Sacken (Entom. ]Month. Mag., xxvii., 37, 

 1891) are worthy of quotation. In separating his Eremoch.eta from the 

 jSTemocera and the rest of the Braciiycera, he says, " 1. The eyes (in the 

 " male) are predominantly holoptic; exceptions are either only apparent 

 " (as subcontiguous eyes, or, in the Sanjida', approximate eyes in one 

 " genus, and absolutely contiguous ones in the very next one) or very 

 " rare {Xylo^phagiis, with Ijroadly dichoptic eyes in both sexes, some 

 " Australian Chiromyzm, Hermetia, and some others may be considered as 

 "exceptions; but even Xyla'pliaxjiLS has in Comomyia a close relative, 

 "which is holoptic; and so has Hermetia in its Australian relative 

 " Massicyta *) ; 2. bisected eyes, with larger facets above than below (in 

 " the male) are of very frequent occurrence ; 3. eyes of variegated colour 

 " are more common in this Section than in any other of the whole order of 

 " Diptera, principally in the Stratiomyldm and Tahanidce ; 4. the antenna? 

 " in the group Ercmochmta are characterised by what T should call a 

 " morphological restlessness ; there is no other group of Diptera in which 

 " the structure of the antennae varies so much, even in closely related 

 " genera. These various forms offer a complete transition from the thread- 

 " like antennas with homologous flagellar joints, characterizing the Nemocera 

 " (such antennas occur, for instance, in Siihula varia, and in Xylophagns), 

 " to the disc-and-arista type, which becomes so common in the other 

 " great division, the Cyclorrhapilia. This transition is effected by the 

 " joints of the proximal portion of the flagellum tending to coalesce and 

 " to form a compound joint in various shapes, while the joints of the 

 " distal portion gradually pass into the form of a simple bristle. Portions 

 " of the antennae are often beset with more or less long and dense hairs, 

 " but the analogue of what I called sensitive hairs in the Nemocera, forming 

 " a verticil, a pencil, or a plume, does not occur here ; 5. There are three 

 " well-developed pvlvilli, which is one of the most characteristic features 

 " of the Bremochcefa ; exceptions are rare. The legs are generally smooth, 

 " without those bristles and spines that distinguish the AsiUdce, and, in a 

 " lesser degree, the Bomhylidai and Therevidm." 



ARRANGEMENT. 



I have (perhaps wrongly) departed from the usual sequence of 

 Stratiomyidcc, Tahanidm, and Leptida:, in that I have placed the Leptidcc 



* " The genera Psammorycter, Lam-promyio , and Phencus, forming the group Psammorycterina, Loew, have a 

 " narrow front in both sexes, and in this character, as in their whole appearance, seem to mimic the AfiUdci' : 

 " but here again their close relative, TriptotriclM, has a holoptic head in the male." 



D 



