INSECTS AFFECTING PARK AND WOODLAND TREES 389 



The galleries of this insect are very characteristic and may be distin- 

 guished from those of T o m i c u s balsa m ens Lec. 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 galleries of the spruce infesting species, 

 while the balsam borer frequently cuts nearly half of the diameter of the 

 primary gallery from the sapwood. The general character of these gal- 

 leries is well shown in the accompanying illustration which represents the 

 central chamber, the transverse primary or egg galleries diverging there- 

 from, together with 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 some- 

 times excavated partly in the sapwood. Several of the egg chambers may 

 also be seen. 



Distribution. Dr Hopkins states that this species is evidently widely 

 distributed over North America and doubtless occurs where its food tree is 

 indigenous. It has been recorded from New Hampshire to Alaska, and 

 Georgia, and in West Virginia it appears to be confined to the Canadian 

 life zone of the spruce area, since it has never been met with in cultivated 

 spruce or in other life zones. 



Associated insects. Dr Hopkins records having found the following 

 species associated with this insect in spruce: Homalota species, Bapto- 

 linus longiceps Fabr., Paro mains bistriatus Er., P. diffi- 

 cult s Horn, Epuraea truncatella Mann., H y p o p h 1 o e u s p a r a 1- 

 lelus Melsh, and H. thoracicus Melsh, and a Tenebrionid larva. 

 He also obtained a Dipterous larvae from the galleries of this borer. 



Natural enemies. The following predaceous insects were observed by 

 Dr Hopkins either in association with this borer or preying on it : T h an- 

 as i m u s trifasciatus Say, T. d u b i u s Fabr., P h y 1 1 o b a e n u s 

 dislocatus Say, and a Clerid larva. 



The following parasites were reared by Dr Hopkins from this species 

 or collected by him from infested logs or trees: Spathius clari- 

 pennis Ashm., Caenophanes pityophthori Ashm., Cosm o- 



