THE LARCH BUG. 423 



XXV. The Larch Buy, ''Aphis" or '' BUghC (Chevmes laiicis). 

 By Dr W. ScHLiCH, Professor of Forestry, Cooper's Hill 

 Engineering College, Staines, Surrey. 



Every Scottish forester will halt when the dreaded name of the 

 " Larch Bug " {Chevmes laricis) reaches his ear, because this little 

 insect is known to be one of the most deadly enemies of the larch 

 tree. Owing to the attacks of this pest young larches are often 

 injured for life, and soijietimes killed outright; moreover, the 

 wounds produced by it in the bark are probably one of the chief 

 means by which the larch cancer (Peziza Willkommii) establishes 

 itself, the result being that in many parts of Scotland the produc- 

 tion of larch has become alaiost impossible. 



Under these circumstances the ^Members of the Society will no 

 doubt be interested in the following information : — 



There ai-e several species of Chermes, and amongst them ai-e 

 the two forms, C. laricis, hitherto observed on the larch, and 

 C. ahietis, which forms the spruce galls. A Professor Blachmann 

 noticed that the females which emerged from the spruce galls did 

 not deposit their eggs on the spruce, but he found about that time 

 numerous eggs dejDOsited on the needles of young larches. This 

 induced him to make a number of experiments, and amongst 

 others he brought together, under thin nets, some spruce galls 

 ready to open for the flight of the females — - 



(1.) with branches of spruce only. 



(2.) „ „ larch 



(3.) ,, ,, spruce and larch. 



After a while it was observed that the females had deposited their 

 eggs, just as in the open, but only on the Larch branches. Pro- 

 ■fessor Blachmann maintains, in consequence, that C. laricis and 

 C. abietis are in reality only one and tlie same species, which lives 

 alternately on larch and s^iruce — in other words, that the females 

 which leave the spruce galls about August lay their eggs on the 

 larch, where they are hatched, the insects remaining there over 

 winter. These either return to the spruce in the spring after 

 having developed wings, or they produce a fresh " winged " 

 generation, which returns to the spruce. 



It has frequently been noticed that the C. laricis has been 

 specially numerous whei'e spruce and larch are growing mixed 

 together, or in woods at a short distance apart. On the other 



VOL. XII., PART III. 2 F 



