E. T. CRESSON, JR. 
29 
The known species of this semis readily divide into two well- 
marked groups, which are here given subgeneric i-ank. They 
are characterized by the number of extensor bristles on the mid- 
dle tibiae and are very constant in this respect. The arrange- 
ment of the facial liristles and of the abdominal markings are 
also of some value, but are not as constant. 
Systematically the species may be arranged as follows: 
Middle tibiae with three extensor bristles (Notiphila). 
Aliddle tibiae of male not ciliate beneath (rfparfo -group). 
Thorax unicolorous, without irrorations or stripes riparia 
Thorax more or less irrorated or striped. 
Mesonotum irrorated punctifera 
Mesonotum faintly, if at all striped bicolor, erythrocera 
Mesonotum distinctly striped. facialis 
INIiddle tibiae of male ciliate beneath (cf ?ie?'ea-group) . 
Mesonotum, at least laterally, distinctly striped. 
Abdomen of male normal, not arched virgata 
Abdomen of male narrow, arched, with fifth segment markedly de- 
veloped vittata, nudipes 
Mesonotum not striped. 
Abdomen ovate, with or without two series of triangular spots. 
loewi, lloridensls 
AI)domen rounded, with or without series of elongate spots. 
- biseriata, cognata,^fulvimana 
IMidclle tibiae with four extensor bristles {Agrolimna). 
Fifth abdominal segment of male convex above, not armed. 
Alesonotum not striped. 
Abdominal markings broad, not attenuating laterally, more or less 
shining scalarls, atrlpes, occldentalls 
Abdominal bands attenuating laterally olivacea, macrochaeta 
Mesonotum distinctly striped .pulchrifrons, frontalis 
cifth abdominal segment of male concaved above, attenuated, and armed, 
at a,nex. with two long bristles bispinosa, furcata 
Table of Species 
A. Middle tibiae with three extensors; facial bristles confined to lower half 
of face { Notiphila) . 
1. Bristles of legs weak and minute; abdomen of male shrunken on dorsum, 
and middle tibiae ciliate beneath (Nearctic species). . . .nudipes p. 43. 
Bristles well developed 2 
2. Mesonotum distinctly striped, at least with a broad lateral stripe 10 
Alesonotum not distinctly striped 3 
TRANS. AM. ENT. SOC., XLIlI. 
