FAMILY SCOLYTIDAE - 569 



The deodar bark-borer passes throu^^h the winter either as a larva at 

 the end of its gallery in the bast layer of the tree or as 



Life History. a mature beetle in the thicker parts of the old bark of 

 deodar-trees. The beetle bores into this old bark to 

 obtain a shelter from the cold of the winter months, and hibernates in this 

 position. As soon as the first warmth of spring makes itself felt the over- 

 wintering larvae change to pupae in their galleries, and then, in a week or ten 

 days, become mature beetles and bore their way out of the tree and seek 

 other trees in which to lay their eggs. A little before the latter beetles issue 

 the mature beetles which have passed the winter in the old bark of deodar 

 trees come out and seek suitable trees in which to oviposit. The eggs laid 

 at this period are those of the first generation of the year. The exact time 

 at which egg-laying begins varies according to whether an early or late spring 

 is experienced. When a very early spring has followed a dry winter the 

 beetles commence operations early in April, and female beetles which have 

 wintered as such may be found boring into trees to lay eggs about the second 

 week of the month. After a long cold wet winter followed by a late spring 

 the Scolytus beetle will not commence laying the first eggs of the vear before 

 the fourth week or end of April. 



The beetles pair outside the tree. The insect's method of attack from 

 the outside and its operations within the tree are constant and are easily 

 recognizable. As is usual with the bark-borers of this family, the female 

 commences by boring a small "shot-hole" through the bark in order 

 to reach the bast layer. This may be made anywhere on the tree (save in 

 the smaller branches of the crown, which are not attacked), but the insect 

 usually chooses a projecting flake of bark in order to screen itself. In the 

 case of small saplings it bores in beneath a branch at the juncture of the 

 latter with the main stem. On reaching the bast layer the beetle carries 

 its gallery in an upward direction parallel to the long axis of the tree. The 

 gallery is made mainly in the bast layer, but it also grooves more or less 

 deeply the sapwood : it is deeper and stronger at its commencement than at 

 the upper end. The gallery so made is the egg-gallery ; it is from two to three 

 inches in length and is carried upwards in a series of serpentine curves, first 

 to one side and then to the other (cf. frontispiece and pi. Iviii). The egg- 

 galleries made in the boles of large trees are usually shorter than those made 

 in saplings, poles, and branches. On either side of the egg-galler}', as she 

 gnaws it out upwards, the beetle bites out small indentations in the wood, in 

 each of which she places an egg surrounded by small fine particles of wood- 

 dust ; these egg-notches do not begin quite at the bottom of the egg-gallery, 

 a small portion of it being left entire ; they are, however, always made right 

 to the extreme upper end, the number cut on either side being approxi- 

 mately identical. As the gallery progresses upwards the beetle keeps it 

 quite free from particles of wood by shovelling out with her legs all the 

 wood-dust, etc., eaten out in constructing it. This dust she ejects through 

 the entrance-hole in the bark ; a portion of these wood particles is also passed 



