150 ECONOMIC ENTOMOLOGY 



cluster of 40 to 50 yellow eggs on a spruce needle. The eggs are 

 extruded from the abdomen but the parent Chermes remains over them 

 until dislodged after her death by wind or rain. The winged form often 

 oviposits near the gall from which it emerges. A different species of 

 host plant is never sought by this Chermes. In about two weeks the 

 young "stem-mothers" hatch from these eggs and seek a protecting 

 crevice in the surface of the spruce bud where they can spend the winter. 

 These wingless forms develop in the spring and become full grown about 

 the last of May when they lay a cluster of 140 or more eggs. From 

 these eggs hatch the young that inhabit the gall and are known as the 

 "gall generation" with which we started the cycle" (Patch). 



Spruce Gall Aphis {Chermes similis Gill.). — (Consult Bull. 173, 

 Maine Agr. Exp. Stn.). Abundant locally on black, red, white and 

 Norway spruces, producing loose terminal galls and scraggly deformed 

 twigs. The galls open about July ist and the winged flocculent mi- 

 grants oviposit on spruce. 



Control. — Spray in early spring while trees are dormant with whale- 

 oil soap (i lb. to 2 gal. water). Black Leaf 40 (i to 800) added to 

 soap (i lb. to 4 gal. water). 



Pine Bark Aphis {Chermes piniccrticis Fitch). — A common enemy 

 of cultivated pines, appearing as flocculent white masses upon the green 

 bark of the more tender parts. 



Control. — Spray in late April or May with fish-oil soap or kerosene 

 emulsion. 



DOUBLE-HOST APHIDS 



Following is a partial list of double-host Aphids: 



Chermes abieticolens on spruce = Chermes pinifoliae on white pine. 

 Pemphigus tesselatus Fitch on alder = Pemphigus acerifoliae Riley on maple. 

 Pemphigus balsamiferte on cottonwood = Pemphigus betae on beets. 



Eriosoma pyricola on pear = Eriosoma pyricola on elm. 



Eriosoma lanigera on apple = Eriosoma americana in part on elm. 



Eriosoma americana on plum = Eriosoma americana on Juneberry. 



Eriosoma ulmi on English elm = Eriosoma fodiens on currant. 



Hyalopterus arundinis on plum = H. arundinis on reed grass, cat-tail. 



Phorodon humuli on plum = P. humuli on hop. 



Aphis avenae on apple = A. avenae on oats, cat-tail, etc. 



Aphis sorbi on apple = A. sorbi on plantain. 



Aphis pruni on plum = Aphis cardui on thistle. 



Aphis peril on oleander = A. lutescens on milkweed. 



