I70 TRANSACTIONS OF ROYAL SCOTTISH ARBORICULTURAL SOCIETY. 



The male of Pityogenes quadridens, in addition to the large 

 curved tooth of P. bidentatus, has an additional smaller tooth 

 on the lower third of the apical declivity. 



As regards the pattern of the brood-galleries bide?itatus and 

 chalcographies may be distinguished thus : — 



P. bidentatus 



Polygamous. 



Mother-galleries radiate from the 



pairing-chamber in a more or less 



star-like pattern. 

 Pairing-chamber visible on the outside 



of the wood and the inside of the 



bark, and the mother-galleries 



visibly meet in it. 

 Mother and larval galleries cut into 



the outermost wood. 

 Larval galleries come away from each 



mother-gallery, not close together 



but at some distance apart from 



one another. 



P. chalcographus 



Polygamous. 



Mother-galleries radiate froirT the 



pairing-chamber in a more or less 



star-like pattern. 

 Pairing-chamber generally hidden in 



the bark, and the mother-galleries 



seem to be quite separate from one 



another. 

 Mother and larval galleries mark but 



do not cut distinctly into the wood. 

 Larval galleries come away from 



each mother-gallery close to one 



another. 



The foregoing differences have to be regarded as typical, but, 

 of course, exceptions are met with. 



There are two other bark-borers of spruce, one of them very 

 rare in Britain and the other only doubtfully recorded. Careful 

 search might reveal them, and they are worthy of mention here. 

 They are Pityopthorus micrographus, Gyll., and Polygraphus 

 pubescens, Bach (polygraphus, L.). 



P. micrographus is smaller than P. chalcographus ; it has an 

 elongate appearance, and is brown in colour. On the front 

 part of the thorax there are minute excrescences or tubercles 

 arranged concentrically. The declivity at the hind end of the 

 beetle shows a distinct furrow on each side of the suture; no 

 teeth are present on the declivity in this species, but a good 

 lens will bring out minute tubercles down the edges of the 

 furrows ; if the insect be viewed in profile, it will be seen that 

 the suture and the side edges of the furrows are equal in height 

 and slope downwards at the same angle. The beetle is 

 polygamous and the mother-galleries, several in number, run 

 out in stellate fashion from the pairing-chamber; there is a 

 tendency for the mother-galleries to take a somewhat horizontal 

 direction. Pairing-chamber, mother-galleries, and larval galleries 

 cut markedly into the outermost wood. 



