64 
vears later they appeared at Hayden, as before stated, having occu- 
pied this time in traversing a distance of about 30 miles. 
The second migration is indicated by two records only—one at 
Hamilton, in 1895, and the other the brood which crossed the Bear 
River and was observed at Lay the same year. Judging from the 
locations where these records were made and the unusual circum- 
stances already mentioned, the direction of travel of this brood was 
more northerly than its predecessor. The records were both made in 
the same year,:and the fate of the brood is uncertain, except that it 
may have become established in the Wilhams River Mountains. It 
was reported to us last summer that the insects have been there for 
SZ 
My, 
=> SSO y | \\/ 
“ps < | “lh Maly wh ny 
\ 
Tie “9 ow 
272 zs / f 
/902 7HAMILTO ey “as vat I\N 
GODA~ (Rk 
EN \\ NIK NG e 
Ly, DUNKLEY 
wu el all BZ 
My, 747 / an = ee Be 
Fig. 6.—Map showing territory infested by Anabrus simpiex in Colorado (original). 
the past ten years, which would agree within one year with the advent 
of this brood. 
In the third great wave we may include the two braode which 
passed through Hamilton in 1900 and 1902, respectively. They both 
passed into the Willams River Mountains and were not observed 
again, so far as we discovered, until the unprecedented migration of 
the past summer. 
Some points with regard to this migration must remain in doubt. 
Whether it was the result of the accumulation of the three broods 
which passed through Hamilton in 1895, 1900, and 1902, respectively, 
or two, or only one of these, is uncertain. It would seem as though 
the last two, at least, must be contributing factors. In any case the 
individuals of these previous broods succeeded in giving rise to count- 
less numbers this summer. 
All of this year’s migrants had their home in the Williams River 
