206 A7inals Entomological Society of America [Vol. XIII, 



surface. This joint appears to be immovably attached to the 

 head. The second joint is longer, attached to the first by a 

 movable joining, and bears a coronet of bristles on its anterior 

 surface. The third joint is the largest, being twice as long as 

 the second, somewhat broader, and laterally compressed. It 

 is attached to the second joint by an immovable attachment 

 formed by parts fitting together like saw teeth. In addition to 

 the three jointed arista, this joint bears structures which are 

 apparently sense organs, consisting of openings leading to small 

 internal cavities. Each such opening is protected by a ring of 

 bristles pointing outward towards a common center. This 

 joint also appears to be porous and sponge-like, the pores being 

 much smaller than the openings to the sense organs. All three 

 points are covered with short, fine pubescence. 



The arista (Fig. 8) is three jointed, all the joints movable, and 

 pubescent. The first two joints are short, cylindrical, the 

 second about twice as long as the first. The third joint is 

 long, somewhat larger at the base and for the basal third, 

 tapering from there to a fine hair-like point. The spines appear 

 to be different from ordinary spines and may function as sensory 

 hairs. 



The discussion of the mouth parts will be left for a later 

 publication as they appear to show no characters of value to 

 this work, but do show some interesting anatomical features 

 that need further study. 



THE THORAX. 



Of the thoracic segments, the first and last are greatly 

 reduced, the mesothorax forming the greater part of the whole. 

 The dorsum of the thorax, with the exception of the two anterior 

 swellings, is the mesonotum. The two anterior swellings or 

 the humeral callosities (hcly) are the upper portions of the 

 pronotum. (Figs. 10 and 12). Anterior to the base of the 

 wings a suture crosses the mesonotum, the transverse suture 

 (trsu), which separates the anterior region or prasecutum (prs) 

 from a posterior region, the scutum (sc). Above the halteres 

 another suture crosses the mesonotum separating the scutum 

 from a posterior, somewhat triangular region, the scutellum 

 (scl). (Figs. 9 and 12). The mesonotum bears two distinct 

 rows of large, strong bristles which diverge slightly posteriorly 

 (Fig. 9). Each row consists of five bristles arranged two on 



