BIOLOGICAL, RECONNOISSANCE AT FLATHEAD LAKE. 151 



startling, the more as the species seemed to be different from all known 

 to occur in North America. He also says: "I cannot hut 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 th» 

 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 sufticient marks of dis- 

 tinction to be considered even as separate races. 



Since capturing these specimens I now recall an occasion when fv 

 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 



