Tachinidae. 43 



the thickening stretches longer out to two thirds of the length, rarely 

 the arista is thickened almost to apex. The relative length of the 

 arista varies not little. The second antennal joint has some bristles 

 on the front edge, of which sometimes one is specially strong. The 

 arista is most often bare, sometimes pubescent or short-hairy or 

 fmally shorter or longer plumose in the whole length or in basal 

 part. The mouth parts are of the Muscid type; an oral cone well 

 developed; clypeiis horse-shoe-shaped or more elongate and more 

 or less forceps-shaped; it has generally a less chitinised, sometimes 

 longitudinally divided part above. Palpi thread-like or more or less 

 clavate, sometimes small or quite rudimentary. Proboscis short, 

 of medium length or somewhat long, with a well chitinised semi- 

 tubular basal part and smaller or larger oval labella. Labrum and 

 hypopharynx present, stilet-like. In some genera the proboscis is 

 very long and slender and the labella more or less elongated to very 

 long and geniculate towards the basal part. ■ — Thorax rectangular, 

 sometimes quadratic or nearly; pro- and metathorax small. The 

 postscutellum of mesothorax is by a transverse impression divided 

 into an upper and a lower part; in some groups (Tachininae, Dexiinae, 

 Phasiinae) the upper part is distinctly or strongly convex and pro- 

 truding, the postscutellum thus being biconvex, but in other groups 

 {Rhinophor inae^ Sarcophaginae, Calliphorinae) the upper part is 

 small, not convex and not or slightly protruding. The bristles are: 

 acrostichals, generally three præ- and three postsutural, only quite 

 exceptionally more; the most normal number of three on each side 

 of the suture is often reduced more or less down to only a præscutellar 

 pair or none at all ; especially the præsutural are of systematic interest, 

 and when reduced it is the third pair which disappears first, the 

 middle pair is the most constant. Dorsocentrals, likewise generally 

 three præ- and three postsutural; also these bristles may be more 

 in number, or on the contrary, reduced. The intraalar bristles are 

 three postsutural or fewer, and one or no præsutural. Just at the 

 margin there is a varying number of larger or smaller supraalar 

 bristles behind the suture and one anterior to the suture, the præ- 

 sutural bristle. On the humeri there are more or fewer humeral 

 bristles, and behind the humeri one to three posthumeral bristles, 

 the place of the exterior in relation to the præsutural bristle being 

 of systematic importance. On the postalar callus generally two 

 postalar bristles. In the præsutural depression are two notopleural 

 bristles and sometimes besides one or two smaller {Gonia, Sarco- 



