The Coleoptera collected by the Canadian Arctic Expedition, 



1913-18. 



FOREST INSECTS. 



The Families IPIDAE, CERAMBYCIDAE and BUPRESTIDAE. 



By J. M. SwAiNE, 



Chief, Division of Forest Insects, Entomological Branch, Department of Agriculture, Ottawa. 



The forest insect collection was made principally at " Camp creek " and 

 along the adjoining river banks, on the east side of the Coppermine river, 

 Northwest Territories, just below Sandstone rapids. Only a few isolated 

 specimens were obtained in other localities. Along the river near Sandstone 

 rapids is the northern limit of forest trees and to examine this Mr. 

 Johansen made a special trip of over 50 miles. The trees here are white 

 spnice, mostly stunted and growing in a very open stand, as is well shown 

 in the accompanying illustration. Plate I. The examination was made in. 

 February at a temperature of about 50 degrees below zero. In addition to 

 pieces of bark containing many dead beetles a section of a trunk and part of a 

 dying branch were brought back by Mr. Johansen. 



A large number of trees were dead or showed dead and dying parts, and a 

 superficial examination of these suggested that many of the dead standing 

 trees had been killed by the bark-beetles whose galleries were extremely abundant 

 on the wood surface wherever this was laid bare. 



Of the bark-beetles a species of Dendroctonus was found at the base of 

 one dead tree; Polygraphus rufipennis Ky. and Pityophthorus nitidus Sw. appar- 

 ently occurred in abundance, while an undescribed species of Carphoborus 

 was probably less numerous and is represented in the collection by only two 

 specimens exposed in a tunnel in one of the specimen sticks while removing 

 the bark in the laboratory. Polygraphus rufipennis and Pityophthorus nitidus 

 were the most numerous in the dead trees and occurred throughout the trunk. 

 Usually they were well chitinized and dark in colour. These species were 

 found chiefly in timber of medium size, rarely in very young oi' very old trees. 

 The Dendroctonus beetles came entirely from the base of one large spruce which 

 also carried the two smaller species (Polygraphus and Pityophthorus) in the 

 upper part. There were many adult Dendroctonus beneath the bark, chiefly 

 in cells in a compressed layer of frass lying upon the surface of the wood. They 

 were all very light in colour and had died before maturity. Mr. Johansen 

 believes that all these beetles were dead when he collected the wood. The 

 cause of their death was not apparent, but was probably due to adverse weather 

 conditions. 



Cerambycid tunnels cut by larvse of several species were also abundant 

 in these dead trees, and had apparently been responsible, in part, for their 

 death. The larger trees were usually quite without bark or had retained it 

 only in patches, particularly about the base of the trunk. The wood surface 

 showed many surface tunnels of cerambycid larvse, and although no living 

 larvse were found, several dead adults of Mereum proteus Ky. were taken from 

 these tunnels beneath the bark. Larval skins were found and dead larva 

 which had apparently been killed by parasitic hymenoptera whose cocoons, 

 usually empty, were found beside them. The galleries of wood-boring ceram- 

 bycid larvse were also numerous in these trees, and several dead adults were 

 taken from the tunnels by Mr. Johansen. 



