AMERICAN DIPTERA. 205 



entirely covering externally the other two. The second and third 

 are united by their bases. The former (B) is triangular, its ante- 

 rior angle produced into a rounded prolongation, the proximal part 

 of its anterior border reflected as a free lobe on the outer side. The 

 third appendage (C) covers the outer posterior part of the second. 

 It consists of three partially separated lobes, one of which sends a 

 long curved arm forward. 



The central vesicle is of ordinary form. The V-shaped bar be- 

 tween its position arms is very large and apparently serves as a brace 

 to keep the walls of the genital chamber apart. The guard of the 

 penis is a simple stylet-like affair with a groove along the upper side. 



Tipula cogiiafu Doane (PI. XVIII, fig;s. 154, 155, 157). 



The eighth sternum is not specially modified, being neither armed 

 nor produced beneath the ninth. 



The tergum of the hypopygium is separated from the sternum by 

 only an indistinct groove. The posterior margin of the tergum is 

 produced into two slender, finger-like processes projecting caudally. 

 The plates of the sternum are separated by a wide membranous area 

 extending the entire length of the ventral aspect back of a narrow 

 anterior connecting bar of chitin (fig. 155). The posterior edge of 

 the sternum is deeply and widely emarginate. The median mem- 

 brane expands posteriorly so as to form most of the posterior margin, 

 and its free edge presents a chitinous thickening. From near each 

 outer angle of the emargination a suture runs forward but ends back 

 of the middle of the segment. The anterior end is very slightly 

 curved outward. The two are the pleural sutures (figs. 154 and 

 155, p. s.). 



There are only two apical appendages on each side (fig. 157). 

 The first (A) is a simple, wide, somewhat fleshy plate, bluntly 

 pointed distally. The other (B) is large and has the curious shape 

 shown in figure 157. It consists of an upper part having the form 

 of a flat, l)lunt hook with the tip curved forward, and of a similar 

 but larger lower part extending downward and curving forward. 



The central vesicle and penis have ordinary forms. The latter 

 makes but a small curve forward. The guard of the penis is sim- 

 ple and stylet like. 



Tipiila caloplera Loew (PI. XVI, figs. 128, 129, 130, 131). 



The abdomen is widest through the seventh and eighth segments 



TRANS. AM. KNT. SOC. XXX. JULY. 1904. 



