PACKARD.] GEOGRAPHICAL DISTRIBUTION OF PHYLLOPODA. 367 
to Southern Utah and Colorado. The exact limits of its distribution 
are given in the First Annual Report of the United States Entomologi- 
eal Commission. 
While we are still quite ignorant of the distribution of insect life be- 
tween the hundredth meridian and the Pacific Ocean, there seems good 
reason, from what little we do know, and from the great differences in 
the dora, and the soil and climate, especially the rainfall east and west 
of the Sierra Nevada, to regarél this lofty range as the general point of 
separation defining two grand zoological provinces. Many groups of 
insects abounding west of the mountains do not occur east, except in 
isolated cases. Of a number of Myriopods found on the Pacific coast 
none occur east, and so of the Arachnida so far as known, and Dr. 
Thorell, who has worked up some of the spiders of Colorado, was struck 
by the general similarity of some forms to those occurring in the 
plateau of Northeastern Asia. Among the insects there are a few 
Pacific forms which closely resemble European species, and which are 
not represented east of the Sierra Nevada. It should be borne in 
mind, however, that the Sierra Nevada does not present an absolute 
barrier, as a considerable number of species occur on each side of if, 
and it is well known that the Rocky Mountains are but a slight barrier 
to the distribution of the animals on either side, the fauna of Colorado, 
Northern Utah, Wyoming, Montana, and Idaho being quite homogene- 
ous, and the fauna of these Territories the same on each side of the 
high mountain ranges traversing them. 
Among the fresh-water Crustacea the Astaci of the Pacific slope, as 
is well known, belong to the European genus Astacus, those east of the 
Sierra Nevada to the genus Cambarus, which is so richly developed in 
the eastern provinces, especially in the Mississippi Valley. 
The distribution of the fresh-water Piyllopoda is of peculiar interest. 
The family Apodide is restricted to the Central province; none are 
found in the Mississippi Valley, and none in California. Of the four 
species of Apus all inhabit the Central province; Apus wqualis lives on 
the plains of the Rocky Mountains, and also at Matamoras, in Mexico. 
Jt is a curious fact that Apus lucasanus Pack. not only oceurs at Cape 
Saint Lucas, Lower California, but is also an abundant species at Ellis, 
Kansas. This is a parallel case to the presence of certain birds at Cape 
Saint Lucas which, as observed by Professor Baird, belong to the Central 
rather than to the Pacific province. Of the genus Lepidurus there are 
two forms (L. couesiti and L. bilobatus) characterizing the plains. JZ. 
couesvi occurs in Northern Montana and in Utah, and is allied to the re- 
cently described Lepidurus macrourus from Archangel, Russia, accord- 
ing to Lilljeborg. 
The eastern limits of the Central province extend to near the 97th 
meridianin Kansas and Nebraska, according to the writer’s observations. 
The following species inhabit this province : 
Limnetis mucronata. Lepidurus bilobatus. 
brevifrons. Apus newberryi. 
gracilicornis. cequalis. 
Estheria compleximanus lucasanus. 
mexicana. longicaudatus. 
belfraget. Branchinecta coloradensis. 
Morseéi. lindahli. 
Eulimnadia texana. Streptocephalus texanus. 
Lepidurus couesii. Thamnocephatus platyurus. 
