CHERMES STROBILOBIUS. 



365 



The larch is the intermediate host of this insect, and the 

 plant-lice on the larch were formerly 

 known as Chermes lands, Hart, (the 

 larch aphis). 



a. Description. 



Imago ? , rather smaller than the 

 preceding, blackish - brown, covered 

 with a white woolly down ; the 

 winged form dirty green, or with 

 the head and thorax reddish-brown. 

 No male is known. 



I. Life- His for y. 



The wingless females pass the 

 winter on the larch, like those of 

 C. alietis, Hart. They lay their eggs 

 and from April to August the aphides 

 sit and feed on the needles, which 

 become discoloured and acquire a 

 peculiar elbowed shape. No gall is 

 formed. They acquire wings in 

 August and disperse to other larches, 

 or to the spruce. When they are 

 abundant, the larches look as if they had been sprinkled 

 with snow. 



c. Treatment. 



Spraying with kerosene-emulsions, soft-soap, limewater or 

 weak solutions of corrosive sublimate. Keep spruce away from 

 larch nurseries. 



4. Chermes sibiricus, Choldk. 



The winged females greatly resemble those of C. coctineus, 

 Etzb., and C. strobilolius, Ktlb. 



The galls, 3-10 cm. long, consist of a but slightly altered 

 bent twig, the needles on the inside of which become thick 

 and woody, but not coalescing as in the former galls. The 

 dark red plant-lice eventually produce winged offspring that 

 fly to the Scots, Weymouth or Cembran pines, and these lay 

 reddish-yellow eggs. Those that stay on the pines, formerly 



Fig. 190. Larch - shoot 

 attacked by Chermes laricis, 

 Hart. {Natural size.") 



a Insects feeding on the 

 needles, which show a 

 characteristic angular bend. 



