PROC. ENT. SOC. WASH., VOL. 24, NO. 6, JUNE, 1922 149 



and the labium along the line g. This discloses the chitinous 

 floor (Phy) of the sucking pharynx with its two posterior cornua, 

 and the dilator muscles of the pharynx (Phy Mel) stretched 

 between the invaginated roof of the pharynx and the edges of 

 the lower facial plate (C/p) which is apparently the clypeus. 

 These muscles form two lateral sheets in the Dolichopodidae, 

 between which is a large apodeme (d) from the epipharynx 

 carrying another set of muscles. The true labrum (Lm) is some- 

 what membraneous in Melanderia but a basal plate (x) inter- 

 venes between it and the clypeus which might belong to either, 

 though, judging from some other forms, it is probably the base 

 of the labrum. A removal of the clypeus, as in figure 4, fully 

 exposes the muscles (Ephy Mel) attached to the epipharyngeal 

 apodeme (d) and inserted on the plate (x). Figure 5 shows all 

 parts removed except the epipharyngeal armature and its 

 apodeme (d). It is here seen that the two sets of prongs (Ephy) 

 are carried on two basal plates (e and/). Each plate is grooved 

 and weakly chitinized along the median line, and the posterior 

 plate (/) supports the great flat apodeme (d) between the bases 

 of its prongs. The contraction of the muscles (fig. 4, Ephy Mel), 

 pulling forward and downward against the base of the labrum 

 (x),- turns the posterior prongs of the epipharynx backward. 

 A lobe on the anterior angle of the posterior basal plate (fig. 5, 

 /) on each side, pressing downward on the posterior angle of 

 the anterior plate (e), turns the anterior prongs forward. At 

 the same time the median flexibility of both plates (e and/) 

 allow the prongs to flare outward. Thus the action of one set 

 of muscles brings about a simultaneous diverging of all the 

 prongs in four directions, forward, backward and laterally. 



Such a complicated epipharyngeal structure as that of 

 Melanderia has apparently not been noted before in any fly, 

 though something similar is common to all or most of the 

 Dolichopodidae. Langhoffer (1902) divided the genera of this 

 family into four groups according to the development and 

 character of the armature of the epipharynx, but he had only 

 two-pronged species, and in a former paper (1888) he had de- 

 scribed the processes as true maiidibles. While we can not 

 accept this idea LanghofFer's study of the organs themselves 

 is interesting. In his first group of genera, typified by Hydro- 

 phorus, he includes forms in which two processes are well-devel- 

 oped and project as long hooks or tusk-like spikes beneath the 

 labrum, recurved in some cases, decurved in others. In 

 Hydrophorus signatus there is a prominent tooth at the base 

 of each large anterior prong suggesting the quadruple structure 

 of Melanderia. In this connection it is interesting to note the 

 great development of the hypopharynx in Aphrosylus venator, 

 which belongs to the Hydrophorus group, the organ forming 

 a long beak-like rod projecting from between the lobes of the 



