AMERICAN DIPTERA. 185 



The penis (fig. 3) can be, in this species, very easily isolated. It 

 is a short, thick, semi chitinous rod, expanded slightly at the middle 

 and ending in a small enlargement. It arises from a biramous, ex- 

 panded base between the arms of the guard. 



The second gonapophyses have the same essential structure as in 

 A. opalizans. Here, however, the lower arm of each is the larger, 

 and is strongly bent upward beyond the middle (fig. 7). The upper 

 arm is nearly straight and bears a small process distally on the 

 upper margin. 



Genus DICRANOIIYIA. 



In this genus the sternum of the hypopygium is rudimentary. 

 The pleura are large and reach the anterior margin of the segment. 

 The apical appendages are large expanded lobes. 



Dicranomyia longipennis Schnm. (PI. VIII, figs. 2, 4). 



The abdomen is slender, the hypopygium forms a small oval en- 

 largement. The eighth segment is very narrow, the dorsal part 

 being a mere transverse band, the sternal part is larger but simple. 



The tergum of the hypopygium is a large trapezoidal plate with 

 the wider base anterior. The pleura are large ovoid plates strongly 

 convex outwardly, reaching the anterior margin of the segment and 

 projecting posteriorly far beyond the tergum. The sternum is mem- 

 branous and rudimentary (fig. 4). 



There are two apical appendages on each side, one ventral, the 

 other dorsal. The ventral one is a large pale oval lobe, as large as 

 the pleurum itself. From its inner basal angle there projects in- 

 ward and forward a slender arm that bears terminally two long 

 bristle like spines projecting posteriorly. The dorsal appendage has 

 the form of a long curved sickle like hook (fig. 4). 



The guard of the penis is an elongate structure strongly decurved 

 at the tip (fig. 2, p, g). Basally it is prolonged into two slender di- 

 vergent arms implanted in the membranous floor of the genital 

 chamber. The penis is simply a curved rod-like tube, somewhat 

 thickened toward the base, arising immediately before the base of the 

 guard between its two roots. 



The second or upper gonapophyses arise from the anterior wall of 

 the genital chamber. They are simply two thin triangular plates 

 set vertically over the guard. Each has the tip prolonged into a 

 small up- curved hook (fig. 2, gon. 2). 



TRANS. AM. ENT. SOC. XXX. (24) JULY. 1904. 



