INSECTS AFFECTING FOREST TREES. 515 



rough, finely punctured and almost striated. It may be distinguished from all other 

 spruce bark beetles by the divided eyes. 



The white pupa is about the same size as the beetle, rather stout and with a 

 tapering abdomen which is terminated by a pair of fleshy, spine-like processes. 



The brown-headed, white grubs or larvre are about yl of an inch long when full 

 grown. The mouth parts and adjacent sutures are dark brown and the. body is 

 usually somewhat curved. 



The galleries of this insect are very characteristic and may be distinguished from 

 those of Touiicus balsaiiicus Lee, which works in balsam, and may therefore be met 

 with in the same forest, by the fact that the wood is rarely scored by the spruce 

 infesting species, while the balsam borer frequently cuts nearly half of the diameter 

 of the primary gallery from the sap wood. The general character of the adult 

 galleries is well shown in the accompanying illustration, figure 13, which represents 

 the central chamber, the transverse primary or egg galleries diverging therefrom, 

 and the minute egg notches. Figures 14 and 15 illustrate the above mentioned 

 features and a number of small dilating mines of the young. It will be observed 

 that the larval mines begin as very slender borings which widen gradually and end 

 in a somewhat broader pupal cell which is sometimes excavated partly in the sap 

 wood. .Several of the egg cha'mbers may also be seen. 



Associated Insects. Dr. Hopkins records having found the following species 

 associated with this insect in spruce: Houialota species, Baptoliiiiis longiceps Fauv., 

 Parouialus bistriatus Er., /'. dijjicilis Horn, Epuraca truiicatella Mann., Hypophlants 

 parallelits Melsh., and H. tlioracieits Melsh., and a Tenebrionid larva. He also 

 obtained a Dipterous larva from the galleries of this borer. 



Xatural Eneuiies. The following predaceous insects were observed by Dr. Hop- 

 kins, either in association with this borer or preying upon it : Tliajiasiiuus trifasci- 

 atiis Say, 'f. ditbiiis Fabr., Phyllobmiius dislocatus Say, and a Clerid larva. 



The folliiwing parasites were reared by Dr. Ho[)kins from this species or 

 collected by him from infested logs or trees: Spathius elaripeiinis Ashm., Licno- 

 pltaiies pityoplitliori Ashm., Cosuiophorits liopkiiisii Ashm., a common parasite of the 

 adult, a species of Eurytoma, a species of Lochitcs, Cccidostiba polygreiplii Ashm., C. 

 deudroetoni Ashm., Dccatomidca polygraphi Ashm. The value of these insects in 

 controlling this borer is shown by the fact that Dr. Hopkins believes them to be the 

 principal natural agents in checking the injuries to spruce in West Virginia between 

 the years 1882 and 1889. 



