524 . 



Hibernation occurs in tlie adult and larval stages ; and in the early- 

 spring (generally April or May) the adults that have lived through the 

 winter become active and begin extending their galleries or construct 

 new ones through the bark of healthy, injured, fallen or standing 

 timber, in which their eggs are deposited. These hatch in a week 

 or ten days. The young larvae bore A^dnding galleries through the 

 inner bark. The length of the larval stage varies considerably ; in 

 the case of the summer brood 9 to 12 weeks are spent in the larval 

 stage, while hibernating larvae remain in that stage for over six months, 

 being inactive during cold winter weather. The pupal stage lasts 3 to 4 

 weeks. From May onwards there is an almost constant emergence 

 of adult beetles until September. The chief period of attack by the 

 adults is during July and early August, but all stages are found through- 

 out the year except the pupae, which do not seem to be present from 

 October until late May. After emergence the beetle may again attack 

 the parent tree, but usually migrates to a neighbouring one. When 

 trees show large numbers of exit holes and the foliage has a yellowish 

 or reddish appearance, it is useless to attempt to save them, and 

 careful examination should be made of all timber in the vicinity to 

 ascertain if the recently emerged beetles have attacked it. The foliage 

 of infested trees may remain green until the majority of beetles have 

 left it, but it usually turns yellow in autumn and forms what is kno\Mi 

 as a " red top " in the following spring. Occasionally swarms of the 

 beetles fly a considerable distance and attack isolated trees or clumps 

 of trees, establishing a new centre of infestation from which succeeding 

 generations will extend in all directions. For the first year or two 

 of infestation but little damage is done to standing trees, but trees left 

 standing are subsequently attacked by other boring insects, fungi, etc., 

 and small trees are soon rendered useless, though large trees may be 

 merchantable for 15 or 20 years. Regions containing large areas of 

 mature or over-mature yellow pine timber are particularly favourable 

 to rapid multiplication and spread of the beetles, especially where 

 heavy storms have broken down some of the trees. 



Natural control of D. brevicomis is exercised to a certain extent by 

 Ichneumonid and Chalcid parasites. Predaceous enemies include 

 Olerid, Trogositid and other beetles and Asilids (robber flies). Certain 

 species of parasitic fungi thrive in the damp gallericvS of the borers, 

 and though little is known of the species that attack D. brevicomis, it is 

 evident that fungi are capable of destroying whole broods of closely 

 related beetles. It is suggested that methods of artificial propagation 

 and dissemination of such a fungus might be worked out with advan- 

 tage. Birds destroy large numbers of wood-boring grubs, and Acarids, 

 such as Seiiis safroi, Ewing, also kill many of them, but whether the 

 propagation and dissemination of these mites would be possible 

 remains to be determined. 



It is admitted that the present artificial methods of controlling bark- 

 beetles are crude, expensive and not altogether satisfactory, but they 

 have given some success in reducing epidemic infestations to normal, 

 or even below normal. Wherever possible, logging operations should 

 be directed to infested areas so as to ensure the cutting of all infested 

 trees after 1st September and to have them through the mill and the 

 slabs destroyed before 15th April. Infested trees growing near lakes 

 or streams should be cut into lengths and put under water ; this will 



