152 DIPTERA OF NORTH AMERICA. [PART IV.' 



The three species belonging here (E. venusia, grapliica, and 

 armillaris) are very closely allied. They have handsomely 

 variegated wings, and bands on the feet differing from the ground 

 color. The male forceps has a very different structure from that 

 of the preceding and of the following groups : it has, on each of 

 the basal pieces, a single, strong, hook-shaped horny appendage 

 (Tab. IY, fig. 16, a, b; forceps of E. venusia). The lower valves 

 of the ovipositor are as long as the upper ones. 



** The fork of the posterior branch of the fourth longi- 

 tudinal vein (containing the third posterior 

 cell) has an angular anterior branch which 

 emits a stump of a vein inside of the discal 

 cell (Tab. I, fig. 18) : subgenus Hoplolabis. 



Only a single North American species, E. armata, belongs to 

 this group. Its forceps is entirely distinct in structure from that 

 of the preceding group (Tab. IY, fig. 14a, 14); its wings are like- 

 wise variegated with brown, but its feet are of a uniformly pale color. 



2. The anterior branch of the fourth longitudinal vein is forked (in 

 other words, when the discal cell is open, it coalesces with 

 the third posterior cell) ; when the discal cell is closed the 

 inner ends of the second and third posterior cells are nearly 

 in one line : subgenus Mesocyphona. 



E. caloptera Say, and E. parva 0. S. belong here ; both are 

 distinguished by the above-mentioned peculiarities in the vena- 

 tion, and their relationship is further proved by the resemblance 

 in the coloring of their body. The position of the two brown 

 stripes on the thorax is quite peculiar, and not to be found in the 

 other Eriopteree ; the feet have dark bands. The forceps of E. 

 caloptera is represented on Tab. IY, fig. 15. The discal cell of 

 this species is generally, that of E. parva always open. When 

 closed in the former species, the shape of the discal cell is such 

 that the inner ends of the second and third posterior cells are in 

 one line ; this is far from being the case with the other Eriopterse 

 with a closed discal cell, as E. venusta, graphica, armata, etc. 

 The shape of the discal cell in these latter species evidently 

 shows that it is the posterior and not the anterior branch of the 

 fourth vein which is forked. 



B. The prsefurca ends in the first submarginal cell, which is longer than 

 the second ; the inner end of the discal cell (or rather, as it is 

 always open, of the second posterior cell), as well as the great cross- 



