226 



THE PROTECTION OF WOODLANDS. 



Spruce-gall and Larch aphis, Chermes abietis-laricis (Figs. 56, 57), a 

 small louse pricking into or just below the side-buds of Spruce and form- 

 ing small green cone-like galls at the foot of the twig developing from 

 such bud, in which colonies of the lice live, and which turn brown and dry 

 when the lice (all ? ) make their exit, some remaining on the Spruce and 

 forming similar galls in the second year, and others flying to and becom- 

 ing white woolly lice on Larch (as Ch. laricis) and probably also those 



Fig. 56- 



Fig. 57- 



Cone-like gall of Spruce Aphis. 



a. The Larch Aphis sucking sap 

 from the leaves, which get bent. 



found on Pine (as Ch. pini) and Silver Fir (as Ch. picece). On this inter- 

 mediate host wingless ? lice are in the following year produced, which lay 

 eggs hatching out winged adults that fly back to the Spruce and there 

 produce a sexual brood ( 6 and ? ), laying eggs upon side-buds and pro- 

 ducing the cone-like galls again. Thus, while wingless ? lice remain 

 always on the Spruce forming galls, there is every year a migration to 

 and from the Larch, bringing the sexual form ( 6 and ? ) back to the 

 Spruce. Hence exterminative measures such as spraying must continue 



