W. Ritchie 181 



run vertically upwards aloiifi the main branch, others run vertically 

 downwards, while others run obliquely. Very frequently the larval 

 galleries run along the branch or twig the base of which has been girdled 

 by the mother gallery. The larval galleries, like the mother galleries, 

 vary considerably in length. The shortest one I have measured was 

 about |- inch in length, while the longest was about 1| inches. 



As is usually the case in monogamous species of Scolytids the female 

 does all the work in the cutting of the mother gallery, right from the 

 entrance hole to its terminating point. In a few cases, however, prior 

 to the disappearance of the female underneath the outer bark I found 

 the male cutting a separate hole close beside her, evidently feeding on 

 the gnawed material. As soon as the female had made a burrow long 

 enough to accommodate herself underneath the bark the male at once 

 repaired to her aid and helped her to widen the mother gallery, following 

 her closely, gnawing first at one side of the gallery then at the other. 

 The chief work of the male however is to throw to the outside of the 

 entrance hole of the gallery the fine bore dust, shovelling it out with his 

 legs. The sexes meet on the surface of the bark. 



In many genera of Scolytids, e.g. Myelophilus and Tomicus, the eggs 

 laid by the female are deposited in notches cut by her, as she bores, at 

 more or less regular intervals along both sides of the mother gallery. 

 In the case of C. abietis the eggs are laid irregularly and no notches are 

 cut by the female; in fact the eggs usually occur in batches. In some 

 cases I found that the female after she had cut a part of the burrow 

 turned back towards the entrance hole and then laid four eggs; after 

 she had laid this set of eggs she again proceeded to tunnel her gallery, 

 returning after a time to lay another set of eggs. The female lays from 

 14 to 24 eggs and takes from 5 to 7 weeks to complete her gallery. 



The larvae when hatched burrow irregularly for some time, eating 

 along the sides of the mother gallery and usually altering its shape. As 

 a result it is often impossible to determine the original shape of the 

 mother gallery after the eggs have hatched. After boring along the 

 sides of the mother gallery for some time the larvae separate and each 

 gnaws a separate burrow in the inner bark layers, feeding on the gnawed 

 material. This gnawed material is passed through the alimentary canal 

 and the undigested waste material fills the burrow behind the larva. 



The mother galleries never penetrate the sap wood but show on the 

 inner bark layers. The young larvae while feeding in their tunnels do 

 not cut the sapwood but for some time prior to pupation they often 

 do groove the sapwood. In other cases the larvae do not groove the 



