APHIDTD.E. 289 



Generation V. — From the jireceding generation we get males and 

 females, both sexes being wingless and exceedingly minute. The 

 fertilised female lays one egg, whence hatches the larva which de- 

 velops into Generation T., and which remains at the base of the bud 

 during the winter, producing in spring the appearance as in fig. 270. 



Chermes abietis (Kalt.) 



In dealing with Chermes viridis it was noted in Generation II. 

 that one portion of the winged specimens proceeded to the larch 

 and a portion remained on the spruce. The latter make galls on 

 the spruce smaller than Chermes viridis, and the galls are said to be 

 ripe in July. In other words, this species always remains on spruce. 



ChEUMES STROBILOBIUS (Kalt.) 



It is quite possible that this species has, by the practical man in this 

 country, been hitherto confounded with Gh. abietis. The structural 

 features, as 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 the difference in the structure of the galls. In 

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

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

 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 " (iiherwintern) of the two species, in- 

 asmuch as in C. abietis the stem-mother {Fundatrix) passes the winter 

 at the base of the bud, whereas in C. strobilobius 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. 



As regards the life-history of this insect, it may be said that in a 

 general way it compares with Chermes viridis. One chief point may 

 be noted — viz., the wintering stage of Generation III. In Cli. viridis 

 this stage hybernates on the bark of larch and deposits green eggs in 

 tlie spring. In Ch. strobilobius the wintering stage is at the base of 

 larch buds, the eggs are of a light brmon colour, and the mother free 

 from wool. 



T 



