9 
we may not find this characteristic present with more typical Isosomas. 
This supposition is to a certain extent supported by the fact that an 
examination of certain of Portschinsky’s species of Russiau Isosomas, 
sent us by Professor Portschinsky some years ago, shows that his 
I. apterum and I. eremitum belong to the smooth Philachyra group, 
and that the former, as the name shows, is wingless. It may further 
be considered suggestive that only females of apterwm were received 
from the Russian writer, while both a male and a female of eremitum 
were received. Does this not immediately hint at a possible alterna- 
tion of generations with these two so-called species? This coincidence 
further suggests that Philachyra may be a valid genus after all, even 
though we are able to separate it from Isosoma by no other morpho- 
logical character than the smoothness of the integument. 
ANALYSIS OF THE SPECIES OF ISOSOMA. 
Females. 
Mesonotum smooth, polished, shining. 
AVAIL mete ste er eeyere seen ais) Sete oe Sia earls ss aioe grande, form grande 
Wain eSsizeeiisers © hare seth ie ote eee mee Seat Ssmceiarcne es = grande, form minutum 
Mesonotum coarsely, more or less umbilicately, punctured. 
Bronotalispot) wWamtin oe... 2s a see essere ose oa epee iarein a clei = me Selanne bromi 
Pronotal spot moderately large and rather distinct........--....--..----- hagent 
Mesonotum rugulose, shagreened or coriaceous; not umbilicately punctured. 
Thorax nearly smooth, feebly shagreened or coriaceous and more or less shining. 
Central furrow of metanotum incomplete...........--.------.------ websteri 
Central furrow of metanotum complete. 
Metanotal furrow with a complete median longitudinal carina. 
Cheeks very, fall:and hairy wes... -s2%,..-5-----s-56-00-2--- hirtifrons 
Cheeks not especially full and hairy ......-....-...------ maculatum 
Metanotal furrow with no median carina. 
Metanotal furrow shallow and transversely striate........---- elymi 
Metanotal furrow strongly emarginate; not striate....-..-- bromicola 
Metanotal furrow with an incomplete median longitudinal carina... fitchi 
Thorax more coarsely shagreened or finely rugulose, opaque or subopaque. 
Abdomen shorter than thorax. 
Much shorter than thorax, subglobose ..---....--...---..----- agrostidis 
Nearly as long as thorax, oblong oval.........----.-----------. captivum 
Abdomen longer than thorax. 
Pron otal Spot Miniter. — =p ee cio a ore tera ei) 2 sicial= =) sco Seatac hordei 
Pronotal spot large, distinct. 
Second abdominal segment longer than fourth and fifth together 
secale 
Second abdominal segment shorter than fourth and fifth together 
tritict 
Tsosoma (Philachyra) grande Riley (fig. 1). 
Tsosoma tritici Riley, American Naturalist, March, 1882, p. 247. 
Isosoma grande Riley, Ann. Rep. U.S. Dept. Agric., 1884, p. 358. 
This species differs at once from all the other American forms by its 
smooth, polished, and shining mesothorax. Next to hordet it is the 
best known and most important, economically speaking, of the North 
American species. It is the only species of Jsosoma for which a true 
