DAMAGE CAUSED BY ANIMALS. 145 



indicated for the other bark-beetles, will require to be applied in 

 order to prevent its increase at the usual rapid rate. 



71. The Three-striped or Wood-loring Bark-beetle, Bostrichus 

 (Xyloterus) lineatus. 



This timber-destroying bark-beetle, from 0112 to 012 inches in 

 length, has dull yellow-brown elytra, antennae, and legs, with 

 three dark longitudinal stripes (at inner edge, middle, and outer 

 edge) on the outer pair of wings, whence the name lineatus is 

 derived. It has none of the tooth-like projections at the termina- 

 tion of the elytra which have been noted in the other bark- 

 beetles already described. 



This beetle only attacks conifers, but may be found on 

 all species of them. It is chiefly attracted towards recently- 

 felled timber, and only exceptionally attacks standing timber 

 of sickly growth ; it differs essentially from the Bostrichini 

 already described in detail, not only in its habits and life-history, 

 but also in being one of the insects classifiable as being technically 

 injurious to timber. 



It swarms very early, in March and the beginning of April, 

 and at once proceeds to attack the timber then usually lying here 

 and there throughout the woods, the female boring an entrance- 

 hole, at right angles to the axis of the stem, into the sapwood and 

 the timber for about T6 to 2'0 inches, and then proceeding to form 

 a horizontal main gallery, or, not seldom, two on each side, (follow- 

 ing the periphery in the direction of an annual ring or zone 

 of wood), on the upper and lower sides of which the ova are 

 alternately deposited in small pockets or indentations. On coming 

 out of the shell the larvse nourish themselves mainly from the 

 sap which oozes out from the walls of the main gallery, and only 

 bore, at right angles to the latter, quite a short larval gallery about 

 0'20 of an inch in length, which remains constant throughout in 

 diameter in place of increasing with the age of the larva, and in 

 which the pupal metamorphosis proceeds. The whole figure 

 represented by the borings is called a ladder gallery, from 

 the fancied resemblance of the main gallery and the short 

 larval galleries to a single-pole ladder and its rungs. There 

 are no special exit-holes, as the beetles, when full-grown, make 

 their way out from their place of abode by the entrance-hole. 



