BIOLOGICAL RECONNOISSANCE AT FLATHEAD LAKE. 161 
startling, the more as the species seemed to be different from all known 
to occur in North America. He also says: “I cannot but believe that 
some of the northwestern species pass east by the passage above Mis- 
soula, where the principal range of the Rocky mountains ends, and per~ 
haps by the upper parts of the Columbia river. As far as I know, such 
species are, until now, not to be found in eastern Canada or in Maine. Of 
course when species can come east in such a way it is possible that some 
could go west in the same way, and would be, perhaps, modified by the 
climate. So I found it necessary to compare carefully with C. yakima 
the C. hudsonica from Michipicoten and C. aequabilis.” 
From July 7 to 14, 1901, specimens were captured. The insects were 
taken from the log bridge at the outlet of the lake, on which they con- 
gregated. The collection was made gradually. Perhaps a half dozen 
would be seen on the bridge or in the rushes. When these were cap- 
tured or driven off it would be some time before others would assemble. 
During the week’s stay at the lake 26 males and 24 females were taken. 
They were all well colored, showing that they had been out for some time. 
They were not seen at Echo lake, a few miles further to the northwest, 
nor have they been seen anywhere else in western Montana. But drag- 
onfly collecting in Montana has not been carried on very extensively. 
Calvert considers C. yakima the same as C. aequabilis, the eastern 
insect. 
Taking C. yakima at Rost lake indicates that this eastern dragonfly 
has effected passage across the Rockies in Montana, and above Missoula, 
as suspected by Hagen. Later investigations may show the exact place 
in the mountains where the species crossed over. It is quite probable 
that the species has crossed at Lewis and Clarke Pass, whose altitude 
is 6,323, from P. R. R. reports. The waters of the Missouri and of the 
Columbia are but a short distance apart, and the pass is low. Since the 
species has not been seen around Missoula it is likely, if the above pass 
was the passage, that the species has followed the Big Blackfoot through 
the upper part of its course and then passed over to the Swan river, and 
down that to Swan lake, from which opens up the large wooded valley 
in which Rost lake lies. 
It will be apparent to the reader that the dragonfly in question has. 
crossed the Rocky mountains, but that the passage has been from the east 
side westward, and not as Hagen supposed, from west side eastward. 
Further, the passage has been recent, since C. yakima and C. aequabilis, 
although on opposite sides of the range, have not sufficient marks of dis- 
tinction to be considered even as separate races. 
Since capturing these specimens I now recall an occasion when @& 
single specimen was thought to be seen at the Biological Station. As I 
was passing through a barn lot on my way to lunch I was sure I saw a 
Calopteryx in the weeds some distance off. I had no net, but grabbed my 
hat and made chase. I was sure I had seen one glimpse of a Calopteryx 
but was unable to find it. 
It is hardly likely the species crossed at the Marias Pass, whose alti- 
tude is 8,500 feet. Nor is it at all likely the species crossed over north 
of this, as the mountains are abrupt, high, and the streams very cold. 
If the passage has been any place in the range south of Lewis and Clarke. 
