64 



years later they appeared at Hay den, as before stnted, having occu- 

 pied this time in traversing' a distance of about 30 ndles. 



The second migration i^ indicated by two records only — one at 

 Hamilton, in 1895, and the other the brood AA'hich crossed the Bear 

 River and was observed at I^ay 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 Williams River Mountains. It 

 was rejiorted to us last summer that the insects have been there for 





Fig. 6. —Map showing territory infested by Analivvs simplex in Colorado ( original i. 



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 l)roods which 

 passed through Hamilton in 1000 and 1002, respectively. They both 

 passed into the Williams River ^lountains and were not observed 

 agnin, so far as we discovered, until the unprecedented migration of 

 the ]>ast summer. 



Some points with reg;ird to this migration must remain in (loul)t. 

 Whether it was the result of the accumulation of the three broods 

 whicli passed through Hamilton in 1895, 1900, and 1902, respectively, 

 or two, or onh' 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 vear's migrants had their home in the Williams River 



