2 Platypezidae. 



clypeus does not seem to be separated. If so the Platypezids would, 

 through CaUimyia, in this respect be the group of Aschiza which 

 stands nearest to the Orthorrhapha. Mouth parts small and retracted; 

 labrum and hypopharynx small; no free maxillary lacinia; the maxil- 

 lary palpi one-jointed, thread-like or sometimes clubbed; labium 

 short, with generally not small labella. Thorax rectangular, often 

 rather high, and arched above. Thorax bears bristles of various 

 kinds; there are often uniserial acrostichal and dorsocentral bristles, 

 they are generally short and more or less hair-like, except the two 

 or three last dorsocentrals which are developed as bristles; in Opetia 

 and Platypeza there are no acrostichals, and in Platypeza the dorso- 

 centrals may sometimes be pluriserial ; in Platycnema the acrostichals 

 are biserial. Further there are humeral, posthumeral, a præsutural, 

 more or fewer notopleural, a supraalar (in Platycnema two) and 

 a postalar bristle (or more), and besides there may be more or fewer 

 hairs in the intraalar region; in Platypeza there is no supraalar 

 bristle; all these bristles may vary in development, and sometimes 

 one or another is wanting. The humeral and posthumeral bristles 

 are rather strong in Opetia and Platycnema, in the other genera 

 small to quite small. Thorax is otherwise bare, only in Opetia hairy. 

 Scutellum has a various number of marginal bristles, often four. 

 Pleura bare except for small prothoracic bristles. Abdomen more 

 or less elongated, compressed or cylindrical or sometimes somewhat 

 flattened; it consists in CaUimyia, Agathomyia. and Platypeza in the 

 male distinctly of eight segments anterior to the hypopygium; in 

 the other two genera only six or seven segments are visible, the 

 others may be hidden or reduced; the first segment is more or less 

 short, the following are of equal length until the seventh, which is 

 small or quite small; after it follows a small præhypopygial segment, 

 and then the ninth segment, the hypopygium. The hypopygium is 

 about globular or more elongate, and it is bent in under the venter, 

 except in Platycnema; it shows a dorsal excision with the anal opening, 

 representing the tenth segment; at the end it has a pair of variously 

 shaped end-lamellæ or claws, and below a pair of appendages is some- 

 times seen. In Platycnema it is of another construction. In the female 

 the last abdominal segments are telescopically retractile. The legs 

 are rather normal as regards the anterior pairs, but the hind legs 

 are characteristic for the family in having tibiæ towards tip and the 

 three or four basal joints of tarsi more or less to strongly dilated, 

 especially the- tarsi; only in Opetia they are not dilated. The hind 



