WOOD- WASPS. 



357 



silver fir, and other conifers. All wood-wasps prefer weakly 

 trees, which have heen injured by deer, lightning, or wind, 

 and especially trees felled in the growing season and stripped 

 of bark. They never attack 

 actually rotten wood, or per- 

 fectly sound standing trees. 

 Miss Ormerod relates an in- 

 stance where, at Workington, 

 Cumberland, in 1889, 1,700 

 c. feet of silver-fir valued at 

 £'60 were irretrievably ruined. 

 The damage done is economic, 

 not physiological. 



Fig. 186.— Wood- wasp in the act of 

 boring, exi)oso(l by splitting the wood. 



e. Prolcctive Eide-^. 

 Removal of all high stumps and broken wood. Felling of 

 all weakly or damaged poles and trees in the thinnings, and 

 rapid removal of coniferous timber from the forest. 



2. Sire.v (jiifas, L. {Yellow wood-a-asj)), 

 a. De-'irri/itio/i. 



/»(rt//o 20— 32 mm. (J) to 15 mm. ($) in length; black, 

 head with a large yellow spot behind the eyes ; abdomen (<? ) 

 reddish-yellow, with the first and last segments black, ( ? ) 

 black with the 2 anterior and 3 posterior segments yellow ; 

 legs black, with the knees yellow ; ovipositor nearly as long 

 as the body. 



Lan-d, like that of the preceding species. 



/>. Lifv-}ii story, e/c. 



This species is particularly attached to the spruce, but is 

 sometimes found in silver fir. Its habits arc tlic same as 

 those of *S'. jtivencns, L. 



It is tolerably frequent in Britain, and prefers large 

 trunks. 



The treatment of its attacks is similar to that adopted for 

 S. jiivcncits, L. 



