47 o FAMILY SCOLYTIDAE 



the Finns gcnirdiiina, infested by Polygraphus trenchi, covered with nume- 

 rous tears of resin. In the case of the smaller branches the entrance-hole is 

 usually marked with an elevated circular rim of white resin as shown in 

 fig. 329. This is also the case with the thin-barked Finns gerardiana. 



Another evidence of the attack which is common to both bark- and 

 wood-boring Scolytidae is that masses of wood-dust may be found on the 

 bark beneath the hole, ejected by the beetle from its gallery. This, with the 

 entrance-hole in the bark, is very often the only evidence that trees have 

 lost their vitality, and are therefore no longer capable of answering the attack 

 by an outflow of resin until the later stage at which the needles begin to 

 turn yellow. 



Broad-leaved trees attacked by these bark-boring pests show no easily 

 visible outward signs until the insects have obtained the upper hand and 

 removed most of the bast layer. The}' then begin to flag, and the leaves 

 turn yellow and drop off. Long before this, however, an inspection of the 

 outer bark will show the numerous tell-tale pin-holes (fig. 310) and the 

 ejected wood-dust particles, either protruding in little conical masses from 

 the holes, or in dust beneath the latter. 



The wood-boring forms of the family very rarely kill the tree, only 

 perhaps when they are so numerous that the holes cover the bark from top to 

 base. Their attacks are, however, serious when the insect is in large 

 numbers, as the holes drilled into the timber entirely ruin its outward 

 appearance for sale purposes, even if, as in many instances, the tunnels 

 only penetrate for a few inches into the sapwood. These beetles attack the 

 wood in various stages of dryness. Some will only infest newly felled, 

 wind-thrown, or snow-broken trees, whilst others only tunnel into trees 

 which have lost a certain amount of sap ; finally, others will only oviposit 

 in absolutely dry timber. 



In 1899 the Government of India published a small work entitled 

 Injurious Insects of Indian Forests, in which I had collected such informa- 

 tion as was then procurable on the injurious insects of the Indian 

 forests. The work was mainly compiled from Indian Museum Notes, 

 with some few additions from observations made by myself. In this work 

 the only Scolytidae included were a Polygraphus sp., since described as 

 Polygraph major, Steb. ; Pityogencs scitns, Blandford ; Xylebonis perforans, 

 Wollaston; and undetermined species said to attack Qucrcus incana, sal, 

 I'inns longifolia, and Finns gernrdiuiui. 



Since that date a considerable amount of investigation work has 

 been carried out regarding the relation of this family to the forests of 

 the country by officers of the Department and others and by myself; 

 many new species have been discovered, and valuable records on their 

 economic importance have been compiled. This information is detailed 

 in the following pages. Whilst some of it has been already published 

 in my monographs and bulletins, much of it appears here for the first 

 time. 



