Febmar>% '15] 



GILLETTE: APHID FOOD PLANTS 



97 



NOTES ON SOME COLORADO APHIDS HAVING ALTERNATE 



FOOD HABITS 



By C. P. Gillette and L. C. Beagg 



Chermes cooleyi Gillette and its var. coweni Gillette 



This species and its variety may be said to live all the year through, 

 upon both the Engelmann and blue spruces for one form, and the 

 Douglass fir for the other. The lice upon these trees now are all in 

 first instar stage, none of them having passed through the first moult. 

 Those upon the Engelmann and blue spruces all have their setae thrust 

 into the bark of the twigs where they will develop and deposit eggs 

 in the spring, and these eggs will hatch the second generation which 

 will produce the cone-like galls at the ends of the twigs. Early in 

 July these galls will give out the adult winged lice of this form which 

 will all fly to the Douglass spruce to lay their eggs upon the needles. 

 The young from these eggs hatch, and without growing in size or 

 moulting, will remain upon the needles with their setse inserted along 

 the median line until the following spring. In the spring these lice 

 become mature and lay eggs which hatch into a brood of lice, some of 

 which remain upon the Douglass spruce, while others go to the needles 

 of the Engelmann and blue spruces where they deposit the eggs for the 

 form above described that remains over winter. So each year the two 

 forms of this species migrate, one to the Douglass and the other to the 

 Engelmann and blue spruces. The Douglass spruce should not be 

 planted near Engelmann and blue spruces in a yard or park. 

 Pemphigus hetce Doane 



This insect is a native of the Rocky Mountain region, and is a rather 

 general feeder upon the roots of plants during the summer season. 

 The goosefoot family, especially sugar beets, garden beets and mangel 

 wurtzels, are favorite food plants. Among our native plants and 

 weeds, we have found this louse common upon the roots of Aster, 

 goldenrod (Solidago), Iva xanthi folia, and lambsquarter, Chenopodium. 

 While it does not seem necessary for this insect to take on a fall mi- 

 gratory habit, still, as near as we have been able to estimate, about 

 one-half of the lice acquire wings during September and October and 

 leave their summer hosts and fly to the cottonwoods. Apparently, 

 only a small percentage ever find the desired host. In beet-growing 

 sections it is common for these lice to fly in countless millions, like 

 great swarms of ants, for- more than a month during the warmer por- 

 tion of the day. Since the fall of 1910 we have known that this louse 

 migrates to the cottonwoods,^ in large numbers in the fall to deposit 



1 See twenty-third Annual Report Colorado Experiment Station, p. 98. 

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