THE LARGE POPLAR LONGICORN. 



281 



brown, the latter on the dorsal surface of segments 3 10, 

 and the ventral surface of segments 2 10. 



b. Life-history. 



Season for flight : June and July. 



The eggs are laid in June in crevices in the bark of poplars, 

 especially near the ground. 



The larvae emerge in July and 

 August, and live and hibernate in the 

 wood, pupating in May of the 3rd year. 



The pupae lie head downwards in 

 a chamber blocked with a plug of 

 wood-dust. 



The images emerge in June of the 

 third year. 



Generation biennial. The insect is 

 rather common in a few parts of 

 Great Britain, chiefly in the Eastern 

 Counties. 



c. Relations to the Forest. 



The larvae bore into young, healthy 

 poplars, and also into willows ; aspen 

 and black poplar up to 20 years old 

 are specially attacked. Seedling-trees 

 are liable as a rule to be attacked 

 from their 5th year, and suckers from 

 the 3rd year. 



The larvae make vertical galleries, 



which reach the centre of the tree : these become gradually 

 filled with wood-dust, which is forced out of the tree by the 

 grubs, through a bore-hole, and becomes heaped up at the 

 base of the plants. The stem is attacked near the ground 

 and reacts by developing a large irregular swelling, the bark 

 of which is fissured. Such perforated saplings are easily 

 broken by the wind. This insect is chiefly of importance 

 where poplars are grown on a large scale, as in France. 



Fig. 139. Larval burrows 

 of S. carcharias, L., in 

 the stem of a young poplar. 



(Natural size.} 

 a Plug of boring dust. 



