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 Russian 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 apterum were received 
from the Kussian 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. 
Winged grande, form grande 
Wingless grande, form minutum 
Mesonotum coarsely, more or less umhilicately, punctured. 
Pronotal spot wanting bromi 
Pronotal spot moderately large and rather distinct hageni 
Mesonotum rugulose, shagreened or coriaceous; not umhilicately punctured. 
Thorax nearly smooth, feehly 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 full and hairy 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.. Jitehi 
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 o\ T al '. captivum 
Abdomen longer than thorax. 
Pronotal spot minute hordei 
Pronotal spot large, distinct. 
Second abdominal segment longer than fourth and fifth together 
secale 
Second abdominal segment shorter than fourth and fifth together 
tritici 
Isosoma (Philachyra) grande Kiley (fig. 1). 
Isosoma 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 hordei it is the 
best known and most important, economically speaking, of the North 
American species. It is the only species of Isosoma for which a true 
