October, '09] JOUENAL OF ECONOMIC ENTOMOLOGY 353 



I have seen a few small galls of this species in City Park, Denver, 

 upon spruces brought from the East. 



Chermes laricifolice Fitch. Rather abundant on Larix americana 

 on campus of ^Michigan Agricultural College and at Geneva. 



Chermes pinicorticis Fitch. On Pinus strohus at Lansing and at 

 Albany. It is commonly very abundant in City Park, Denver, upon 

 the same pine. 



Pemphiginae 



Tetraneura ulmicola Fitch. At Lawrence, just beginning to get 

 wings; at Geneva galls very common, some turning red and in these 

 vs^ere many alate lice and pupas. In the green galls all were nymphs. 

 Many galls of this species were also seen at Washington. Have once 

 seen galls of this species in Fort Collins upon an elm from an Iowa 

 nursery, set the foregoing spring. Figs. 1, 2. 



Hmnamelistes spinosus Shinier. The powdery apterous form of this 

 louse was taken in abundance upon the under side of the leaves of 

 white birch at Albany. At Washington the spiny galls were taken 

 from witch hazel (Hamamelis virginica) along with the galls of 

 Hormaphis Jiamamelidis. The galls were reddish, and were packed 

 with lice of about the same color. In each was found a very robust, 

 almost globular, stem-mother and lice of all stages, including the 

 winged form. 



Since my return Mr. 0. G. Babcock. a special student in entomology, 

 on August 2 brought me from the foothills near Fort Collins, at an 

 altitude of 7,000 feet, several leaves of the mountain birch (Betula 

 fontinalis) upon which were colonies of Hamamelistes that seem in 

 every way to agree with the characters of spinosus. This seems 

 strange as the witch hazel family is not known to occur in the Col- 

 orado fauna for the alternate form of this species, which would seem 

 to be necessary according to the careful work done by Mr. Pergande 

 upon this louse in the East. It is possible that the Colorado form may 

 be a distinct species with a different alternate food plant not yet dis- 

 covered. Upon the other hand it is possible that this louse is able to 

 continue from year to year upon the birch. We have found that 

 many lice which have the habit of alternating their host plants are able 

 to continue indefinitely upon one of them. ]\Iigration to a new food 

 plant in early summer seems to be for the purpose of getting away 

 from natural enemies that have rapidly increased upon the winter 

 host, and this habit is probably a comparatively recent development. 

 So it is not strange that in many species we find this migrating 

 tendency failing to be universal among the individuals of a colony. 

 Chermes cooleyi, during early July, almost completely leaves the blue 



