XIX INSECT A : RHYNCOTA 289 



are described by Buckton as "spring cables." ^ The antennae of 

 Ghermes are short compared with those of an Aphis. These 

 hibernating forms on the spruce are all female insects. In 

 the spring they awake to activity, and begin to pierce the 

 young growing tissues at the base of the bud and suck 

 nourishment from them. These punctures cause the formation 

 of such a gall as shown in Fig. 214:, g ; the tissues swell up 

 and form a little green structure which is at first rather like 

 a young cone with scales arranged regularly on it and with 

 little cavities lying below the scales. 



Generation -^^ ®°°'^ *^ *^® insect responsible for this 



II. gall has fed sufficiently on the juices of the bud, 



Still on slie lays parthenogenetically a little cluster of 



pruce. gtalked eggs, and then dies. The larvae which 



hatch from these eggs make their way into the cavities of the 



gall, and remain there feeding on its tissue, gradually acquiring 



their adult winged condition. In August, usually, the perfect 



insects creep out of the gall, which is now brown and woody, 



and the scales of which have separated, exposing the cavities 



(Fig. 214, g). The winged forms which come out are all females, 



and they now take one of the two following courses of action : 



Generation (^^ Some of them stay on the spruce and lay 



III. parthenogenetic eggs which form fresh hibernating 



On Spruce females of Ghermes ahietis ; 



and Larcu. ^g) Some migrate to the larch and there lay 



clusters of stalked eggs (Fig. 216, A and B), which give rise to 



female insects that hibernate on the larch, and are known 



as Ghermes lands (Fig. 216, G). 



Chermes This hibernating female awakes in March, and 



laricis. j^yg parthenogenetic eggs on the larch twig, which 



ly by May have developed into both wingless and 



On Larch, winged female forms. 



Generation "^ he winged forms return to the spruce and lay 



V. V and 6 ■ parthenogenetic eggs there in the summer, and 



On Spruce, these produce both female and male insects — the 



first appearance of males in the life-history. 



Generation Finally, each of these females lays one fertilised 



VI. or I. egg on the spruce in the autumn, which may 



On Spruce, develop into such a hibernating female as was 



described as Generation I. 



1 Mouograpli on British Aphides, by Buckton, vol. iv. , Ray Society. 

 VOL. I U 



