30 PROCEEDINGS: BOSTON SOCIETY NATURAL HISTORY. 
and forceps alike; penes differ but show a common plan of construc- 
tion. 
Basis of grouping : identical external characters, fourth ventral platef 
claspcrs, and forceps. 
Specific characters : penes. 
Group b. 
S. haemorrhoidalis Meigen, S. dalmatina Schiner, S. falculata 
Pandelle (members of the haemorrhoidalis group as recognized by 
European writers). These species agree markedly in external char- 
acters, but may usually be separated by them. Fourth ventral plates, 
claspers, penes, and forceps all differ. 
Basis of grouping: most external characters. 
Specific characters: few external characters, fourth ventral plateSy 
claspers, penes, and forceps. 
Group c. 
S. tuberosa sarraceniae (Riley), »S. tubcrosa harpax (Pandelle), S. 
tuberosa exuberans (Pandelle) (members of the tuberosa group as 
recognized by European writers). External characters furnish both 
good specific and good group characters. A few points are cited to 
illustrate. They agree as follows : the general appearance aside from 
coloration, both genital segments clothed with equally long hair, the 
first without marginal bristles, connecting membrane bears long 
slender bristles in two short lateral rows anterior to the 'humps/ 
They disagree externally most prominently in their color: in S. 
tuberosa sarraceniae (Riley) both genital segments are dull orange; 
in S. tuberosa harpax (Pandelle) both are black; in S. tuberosa exu- 
berans (Pandelle) the first is black, the second dull orange. Fourth 
ventral plates differ, claspers very similar, penes strikingly similar, 
forceps of sarraceniae (Riley) and harpax alike, but differing from that 
of exuberans which is like that of tuberosa Pandelle. 
Basis of grouping: external characters in part, similar penes. 
Specific characters : external characters in part, fourth ventral plates, 
forceps in part. 
Group d. 
Two species, as yet undescribed, are radically different in most 
external characters: fourth ventral plates similar, claspers and penes 
differ but show some similarity, forceps similar. 
