APHIDID.E 



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illustrated by Judeich and Nitsche, do not show any strong salient 

 points of difference, and in the absence of knowledge on the part of 

 the student regarding verification of the alternating stage, it would 

 be well to recognise tbe difference in the structure of the galls. In 

 C. strobUobius we find the galls smaller, globular in form, and in colour 

 resembling the unripe fruit of the wild strawberry. The develop- 



Fig. 300. Winged forms o/Chermes abietis on spruce leaves (enlarged). Found in autumn. 

 This stage should be carefully studied, as it probably may be the sexupura stage. 



ment of the gall is such that leaves do not project beyond the gall. 

 In the German literature it is said that there is a marked difference 

 as regards the " over-wintering " (uberivintern) of the two species, in- 

 asmuch as in G. abietis the stem-mother {Fumlatrix) passes the winter 

 at the base of the bud, whereas in C. strobUobius the creature winters 

 in the top of the bud. It is therefore suggestive that the initial action 

 of the respective insects produces the variation of gall structure. 



