148 PROC. ENT. SOC. WASH., VOL. 24, NO. 6, JUNE, 1922 



bristles, the male does not have the striking tuft on the inner side 

 of the front femur and there are slight differences in the other 

 peculiarities of the front legs. It is considerably smaller than 

 the preceding species, the male measuring hardly more than 

 3 mm. and the female about 3.5 mm. The front and face are 

 green instead of purple and the third vein runs closer to the 

 second than in mandibulata^ curving considerably backward, 

 near the tip of the wing. 



Paratype, Female No. 25241, U. S. N. M. 



MANDIBLE SUBSTITUTES IN THE DOLICHOPODIDAE. 



BY R. E. SNODGRASS. 



A first view of the face of Melanderia mandibulata (pi. 14, 

 fig. 1) gives one a decided shock, followed by a desire to dis- 

 cover by what morphological trick the fly so cleverly imitates 

 the features of a mandibulate insect. But the disguise is a 

 flimsy one. Each labellum of the proboscis (fig. 6) is divided 

 into an upper and a lower lobe (a and ^, c), free terminally, but 

 united basally by an ample infolded membrane. The lower 

 lobe is differentiated again into a basal part (<r) and a terminal 

 part (), the latter of thick, polished chitin and produced into 

 a large, sharp, free tooth turned inward toward the one on the 

 opposite side (fig. 1). These are the "mandibles." The lobe 

 (c] is movably articulated at its base to the basal plate (fig. 6 

 Th) of the labium. This sclerite, called the theca, as in most 

 flies, presents a high median ridge on its inner or anterior surface 

 which gives attachment to muscles diverging to the lobes of 

 the labellum. The fibers on each side are separated into two 

 bundles, the proximal ones being inserted on the upper outer 

 angle of the basal lobe (c] of the labellum, and the distal ones 

 on the inner, median angle of the same lobe, which is united 

 internally to the lower margin of Th by a special median articu- 

 lar condyle. Thus the lobe (f), terminating in the strongly 

 chitinized point (<), can be worked in and out in true mandibular 

 fashion. Figure 2 shows the parts of the labellum in repose 

 with the mandible-like lobes (b) concealed beneath the upper 

 lobes (a). The insect now presents the aspects of an ordinary 

 fly. 



But Melanderia possesses, besides its pseudo-mandibles, 

 other mouth structures of interest which, however, are not 

 visible externally. These are four great prongs depending 

 from the epipharynx (fig. 3, Ephy), in addition to the usual 

 hypopharynx (hphy), which is a strongly-developed, decurved 

 appendage projecting from the lower lip of the mouth within 

 the anterior enclosure of the labium. These parts may be 

 exposed as shown in figure 3 by dissecting off the rest of the head 



