638 REPORT UNITED STATES GEOLOGICAL SURVEY. 



rvhrum from Essex County, Massachusetts, a slight tendency of the ab- 

 domen to become notched, and I shoukl not be surprised to find inter- 

 mediate links connecting the variety atlanis with femur rubrum, but 

 with the evidence now before me, especially the occurrence in California 

 of diminutive short-winged male sjyretus, scarcely distinguishable from the 

 eastern atlanis, the two specimens agreeing well in the form of the ab- 

 dominal tip. I am inclined to the belief that atlanis is simply a variety 

 of spretus. Speculating on the origin of the two species, I should con- 

 sider, that femurnihrumheiug on the whole the more widespread species, 

 that spretus originated from it after it {femur-rubrum) had attained its 

 present distribution, and that spretus assumed its larger size and great 

 length of wing on the hot and dry central plateau of the llocky Moun- 

 tains. 



Practically considered the two injurious forms are the gzumnOi spretus 

 and the g^nvnuQ femur-rubrum. It is the latter which is so abundant 

 and destructive at times in the New England States and Canada, 

 Having known the insect so well for twenty years in Maine and New 

 Hampshire, I am surprised to find in I\[r. liiley's seventh report the 

 suggestion that the femur-rubrum "had been contbunded" with his 

 «i/a«7'.<f, and ''had played the part of a migratory locust in the White 

 Mountain region of Maine and New Hampshire." The form atlanis is 

 a comparatively rare one in New England. During the summer of 1874, 

 '75, and '76, in Massachusetts at least, it has been very rarely met with, 

 compared with the ordinary red-legged locust, and must have been so 

 in 1864, judging by the labels on the specimens in the museum of the 

 Peabody Academy of Science, and I have little doubt but that it has 

 always been a comparatively scarce insect, while the genuine femur- 

 rubrum abounds in countless numbers each summer and autumn from 

 Maine to Massachusetts, and I suppose all over its destructive limits as 

 laid down on Map II. 



I have received a male and female of C. spretus, var. atlanis, from Mr. 

 Henry Gillman, of Detroit, who collected them "near Laughing Fish 

 Eiver, Michigan,* on the south shore of Lake Superior. This river falls 

 into Traine Bay, an indentation of the coast to the eastward of Mar- 

 quette. These specimens measured thus, from head to tip of wings when 

 folded, male l.OS, female 1.10 inches; atlanis from Massachusetts, male 

 1.02, female 1.12 inches ; atlanis from Illinois, male 0.92, female 0.95 inch ; 

 atlanis from California, male 0.99 inch. On the other hand a male G. 

 spretus, normal form, from Iowa, measured 1.30, while an average male 

 from Colorado was 1.31 inches in length. Ten specimens of Iowa sjyretus, 

 the ofl'spring of emigrants from the Kocky Mountains, were slightly 

 smaller and considerably darker than specimens from Missouri, Kansas, 

 and Colorado, approaching slightly but perceptibly var. atlanis and 

 femur-rubrum. I have the idea that if the normal form of spretus were 

 permanently acclimated in the Mississippi Valley, it would change to' 

 var. atlanis. 



I should add that the conclusions regarding the varietal nature I 

 have above stated are written out from notes made two years since 

 after careful examinations, and in 1871, and again in 1875, while I have 

 at the present time of writing re-examined the subject and come to the 

 same conclusion as I held in 1874. 



DOES THE ROCKY MOUNTAIN LOCUST INHABIT THE PACIFIC COAST ? 



Prof. C. Thomas remarks as follows in the Zoology of Lieutenant 

 Wheeler's Survey, p. 892, 1870, concerning the westward distribution 



* Riviere aus Poissous qui rit, of the French Voyageurs. 



