65 2 THE AMERICAN NA TURALIST. [Vol. XXXVI 1 1. 



(b) The form from Honey Lake, -on the extreme western 

 border of the old Lake Lahontan, is also well differentiated, 

 though not in the same way. This lake is extremely shallow 

 and evanescent, having dried up at least twice within the mem- 

 ory of the present generation, and has no doubt been separated 

 from the main body of the old lake since a comparatively early 

 period in the second great decline in size of the latter. The 

 beetles live about the seepage on the lake beach that comes 

 from the hot springs a few hundred yards distant. While it is 

 impossible at present to point out the details which lead to vari- 

 ation in any one direction, it is evident that local conditions, 

 aided by long isolation, have so modified this form that it is now 

 readily separable, in series, from those taken elsewhere. 



(c) The specimens from Humboldt Lake, farther to the east, 

 are more of the type of typical echo, differing but little from the 

 series taken at Great Salt Lake, Utah, whence the species was 

 originally described. While the Humboldt colony must have 

 been separate from the latter for a great length of time, it has 

 been comparatively little differentiated therefrom. The reason 

 for this cannot now be assigned. It may be that the local con- 

 ditions requisite to incite variation were not present, or perhaps 

 the two colonies have simply varied along parallel lines. Though 

 isolation is unquestionably favorable to differentiation, it does 

 not follow that every isolated colony must differ from every 

 other. It is well known that with certain species of Cicindela 

 some colonies produce mostly specimens of one type, others 

 will produce those of another, while a third will be composed of 

 a mixture of both, with all the intergrades. 



(d) The form from Great Salt Lake, to which the name C. 

 echo is properly applied, is not like that from Owens Lake nor 

 that from Honey Lake, though closely approached by the speci- 

 mens from Humboldt Lake. 



(e) On the shores of the small lakes in Wyoming, we have 

 C. u'llhstoni, a closely related form occurring (as far as we 

 know) nowhere else, which according to geological evidence can 

 scarcely have had any communication with the Great Basin col- 

 onies during Pleistocene times. I am inclined to look to a still 

 more remote date for the cause of this phenomenon, and con- 



