86 Second Report on Economic Zoology. 

 The Larch and Spruce Aphis. 



( Chermes uhiefis-laricis.) 



The larch is very frequently damaged ]iy this pest in different 

 parts of the conntry. Buckton records in 1S71, that "the woods 

 in some parts of Surrey were so covered witli the myriads of white 

 tufts spun by these insects that they appeare<l as if slarch liad been 

 dusted over them. Many boughs died back, and in the autumn the 

 trees looked as if they had been scorched." 



The presence of tliis pest (/aricis) is very easily detected when on 

 the larch by the wliite wool excreted by them, and l)y the galls when 

 on the spruce {alieHs) ; larch in some cases looking as if covered with 

 snow. Trees of all ages are attacked by this pest, which sucks out the 

 sap from the leaves, and also the young bark. Schlich figures a 

 characteristic way of damage in the larch, the needles bending over 

 where the Chermes is feeding, and the area around it turning pale. 

 This elbowing of tlie needles is not, however, always noticeable. I 

 have frequently seen trees quite white from this pest, and yet 

 not a single leaf bent ; this was the case in a specimen sent from 

 Northampton "luring the past year. This larch pest is also known as 

 the Larch Bug and Larch Blight. According to Buckton,* Chermes 

 laricis is confined to the larch, but Dreyfus and others have almost 

 conclusively sliown that this species and the Spruce Gall Aphis 

 {Chermes ahietis) are alternating forms of one and the same species. 

 The form on the larcli {C. laricis) is agamic only, but on the spruce 

 there is always one annual sexual generation {C. ahietis), separated 

 from the preceding sexual generation by a series of agamic forms, 

 whicli it appears may remain on the spruce or may migrate to the 

 larch. 



Life-history of C. ahietis-larids. 



The female Chermes laricis pass the winter under the bark of tlie 

 trees and appear in spring. This so-called " queen aphis " hibernates 

 under the leaf scales, often several together, and presents a curious 

 shrivelled, almost dead appearance, and generally resembles the 

 colour of the Ijark. As soon as the buds begin to swell and the 

 spring approaches, they also swell and then throw off their skin, 

 which is retained by the Aphis some days, being attached by three 

 long spirally -coiled hairs. Later, after another moult, the queen 

 becomes silvery white with pale brown tubercles. When fully grown 



* Mono. Brit. Aphides, iv., p. 38, 



