INSECTS INJURIOUS TO CONIFERS. 



167 



and should be tried during the month before the appearance 

 of the moths. Egg-laying takes place in the evening, and it 

 is sometimes worth remembering that the moths can be kept 

 off small patches of trees which it is important to preserve 

 by lighting weed-fires to windward, so that the smoke will drift 

 over. This is not capable of extended application, but may be 

 employed to protect ornamental trees which sometimes suffer 

 severely in the neighbourhood of large Pine- woods. These 

 insects are most troublesome when trees are crowded together, 

 neglected, and grown on unsuitable soil, and, as is usually the 

 case, when the wood is not mixed. 



Pine-beetle. 



Myelophihcs {HyUcrgus) piniperda, the Wald-gdrtner or 

 Pruner of the German foresters, is, next to Gurculio Abietisj 

 the most injurious insect to Pines in Great Britain, over the 

 greater part of which it is very abundant. There are, however, 

 many districts where it does not occur, or has not been observed, 

 but almost any Pine-wood will yield evidence of its presence to a 

 careful searcher. It is a small oblong brown beetle of the family 

 Scolytidcd, or Bark-beetles. 



The female, about the beginning of April, chooses a tree for 

 oviposition. Those selected are newly dead or dying Pines, 

 especially freshly felled timber, unbarked logs and stumps, 

 or trees injured by storms, snow, or fire ; they must have the 

 bark on, and are preferred as fresh as possible, provided that the 

 sap is not actually circulating. Occasionally the beetles make 

 use of Spruce, and, according to Dr. Somerville's observations, of 

 Larch. She commences boring under a projecting scale, where 

 the bark is thick, often on the under side of a fallen trunk, if it 

 is free from the ground, and excavates a gallery in the bast 

 running, with the exception of the entrance which is oblique, 

 along the axis of the trunk. It is from three to four and a half 

 inches long, and takes from three to five weeks to construct. 



The eggs, which may reach 120 in number, are placed in 

 small hollows excavated alternately along its two sides. They 

 hatch in a few days, and the larv© begin to construct lateral 

 galleries at right angles to that of the mother. The larval 

 galleries are at first small, but increase in size with the 

 growth of their inmates and soon take an irregular course. 



