THE SIX-TOOTHED BARK BORER. 



169 



herself; along each side of the gallery eggs are laid in little 

 notches. The mother-galleries, four to eight in number, accord- 

 ing to the actual number of females, run out in star-like fashion, 

 and it may be in a somewhat winding way, from the pairing- 

 chamber. These mother-tunnels show on the inside of the 

 bast, and mark the sapwood, but not deeply. Typically, the 

 position of the pairing-chamber buried in the bast renders 

 the pairing-chamber invisible from the inside of the bast, and 

 thus the mother-galleries, examined on the inside of the bark, 

 appear to be separate from one another, not meeting at a point. 

 The diameter of a mother-gallery is about ^V of an inch. 

 The larval tunnels that run or wind from each mother-gallery 

 are comparatively short, and are close to one another. Pupation 

 takes place at the end of the larval gallery, the pupal beds 

 being in the bark. 



P. chalcographus goes especially on thin-barked parts ; on 

 unhealthy spruce on the higher-up thin-barked parts and 

 branches, and on suppressed young plants, and on felled spruce. 



While spruce (Picea excelsd) is the typical host-plant there are 

 continental records on Pinus sylvestris, Pinus cembra, Abies 

 pectinata, and Larix europaea. 



Other Species that can be Confused with 

 P. chalcographus. 



Confusion sometimes arises between this species and the 

 related Pityogenes bidentatus, the two toothed pine beetle, a very 

 abundant species which, though chiefly limited to pine, is also 

 found on spruce. 



The adults may be distinguished thus : — 



P. bidentatus. 



Larger, T V to r V inch. 



All one colour, black or dark brown. 



The sides of the wing-covers with 

 rows of punctures right to the apex. 



The hind end of the wing-covers of 

 the male shows a broad circular 

 impression with a large somewhat 

 curved or hook-like tooth on each 

 side. 



The hind end of the female has a 

 steep slope furrowed on each side 

 of the suture, but there is no tooth. 



P. chalcographus. 



Smaller, ^ to T V inch. 

 Two-coloured, dark in front and pale 



behind. 

 Sides of wing-covers smooth towards 



the apex. 

 The hind end of the wing-covers of 



the male shows a furrow on each 



side of the suture and three teeth. 



Hind end as in male, but the three 

 teeth are less prominent. 



VOL. XXXI V. PART II. 



