2,^5 



in consequence of the operations of the silver-mining industry, and 

 except some remnants in the less accessible ravines and side canyons 

 only a few scattered trees, or, at best, groups of trees, are left. These 

 trees, already more or less weakened by their isolated and exposed 

 position are preferably infested by this beetle and succumb, one by one, 

 to its attacks. 



In the mode of attack this Hylesinus t^ericeus does not differ from 

 many other bark-boring- Scolytid;ie. The female beetle bores a hole 

 through the bark and constructs a longitudinal gallery just between the 

 bark and the sapwood. During this operation she deposits the eggs at 

 regular intervals along the two sides of the gallery. The young larva? 

 commence to gnaw side galleries, which at first run horizontally, but 

 gradually assume, or at least have a tendency to assume, a longitudinal 

 direction. 



The accomi)anying figure (Fig. 25), which illustrates the work of three 

 female beetles and their numerous progeny, renders all further descrip- 

 tion unnecessary. It represents a small ])iece of the bark of Engel. 

 mann's spruce {Picea engelmanui), collected near Alta, at the head of 

 Little Cottonwood canyon. The whole trunk of the tree was just as 

 densely covered with these galleries as the small sample piece figured, 

 and it is hardly necessary to remark that the tree had already succumbed. 



This scolytid appears to be readily attracted to trap trees, for I saw 

 at the mouth of Big Cottonwood canyon a pile of freshly sawed spruce 

 wood which was densely beset with the galleries, and I have no doubt 

 that a few pieces of wood laid out at the proper season and properly 

 attended to (/. e., decorticated before the larvse are full grown) would 

 protect the living trees for some distance around. 



Scolytid beetles in the imago state are very difficult to distinguish 

 from each other, but in most instances the species can be readily recog. 

 nized from their mode of work; and this proves the importance of 

 giving illustrations of the galleries. There is in the Kocky Mountain 

 region no other pine-infesting scolytid* which constructs galleries 

 similar to those of Hylesinus sericeus. 



The gallery figured above differs radically from those known to be 

 made by other species of Hylesinus, and the following remarks are 

 added as an explanation of this discrepancy : 



The species origuially described by ^Mannerheim as Hylurgus sericeus 

 and subsequently referred by LeConte to Hylesinus can not be retained 

 in the latter genus. In Hylesinus the antennal club is distinctly com- 

 pressed and the front coxte are widelj^ distant; the species live in decid- 

 uous trees, and the gallery made by the female beetle is transverse. H. 



* The followiug species of scolytidii^ were observed in June, 1891, to live on Picea 

 engelmanni in the Wahsatcli Mountains of Utah, at an altitude from 8,000 to 10,000 

 feet: Hyhisfcs macer, Hi/le'tinus sericeus, Dendroctonus rujipennis, Scolytus unisjnuosiis, 

 Tomicus hudsonicHs, Piii/ogenes cariniilatus var., Cryphalm intricatm, C. stfiatulus^ 

 Pitjioph thorns nitidulns. 



