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1878. | Province of the United States. 515 
northwards into the Upper Saskatchewan valley as far as the 
southern limit of trees, there being much less intermixture with 
Canadian forms than might be expected. ,Then crossing the 
Sierra Nevada, and going overland to Oregon, I was able to trace 
the gradual passage of the Californian insect-fauna into the 
Oregonian, with some Canadian forms; and by passing up the 
Columbia river to Wallula, here as well as at Reno in Nevada, 
to perceive the great differences between the fauna of the Pacific 
slope and that of the plains and deserts of the Central province. 
In briefly reviewing the different orders of insects, other than 
Coleoptera,which have been so fully elaborated by Dr. LeConte, 
and certain groups of Crustacea, we will begin with the Hymen- 
optera, and point out a few characteristics distinguishing the 
Central from the Pacific provinces. In 1865 and 1866 a large 
number of Coloradian fossorial Hymenoptera passed under the 
writer’s hands, Mr. Cresson having previously described from this 
material a large number of Coloradian Hymenoptera of all families. 
The richness of the hymenopterous fauna of Colorado struck me, 
and I was impressed with its distinctness from that of the Eastern 
States. I have seen few of these forms from California. Among 
the family of ants (/vrmicide), there is one form characteristic of 
the plains which does not occur on the Pacific slope. This is the 
Pogonomyrmex occidentalis (Cress). I have seen its large hills at 
Brookville, Kansas, and observed them in Colorado and Utah and 
in Reno, at the base of the Sierra Nevada, but not west of that 
point. It ranges, according to Mayer, south into New Mexico, 
and San Luis valley, Colorado. Its nest forming large elevations 
in cleared spaces sometimes six or eight feet in diameter, is one 
of the characteristic sights on the plains. 
Among the Lepidoptera, family Bombycide, there are several 
forms peculiar to the central district, notably the genus Dirphia 
(Coloracia), Hxleucopheus, Gloveria (Mesistesoma), Hemileuca 
Funoand Hera, and Platysamia gloverit. The family is feebly repre- 
sented in the Central province, but richly so by numerous species 
on the Pacific slope, which do not appear east of the Sierra Nevada. 
The Phalenide, or geometric moths, are richly developed in 
the Pacific province, and but poorly in the Central province, 
owing to the absence of deciduous trees; of those found in the 
_ latter some occur west of the Sierra Nevada, and some are peci 
liar to the plains and Rocky mountains. 
VOL. XII.--NO. VII. 36 
