104 TRANSACTIONS OF ROYAL SCOTTISH ARBOR1CULTURAL SOCIETY. 



edge of the excavation gives one of the most reliable characters 

 for distinction from the closely allied forms of P. quadridens. 



Characters of the Wing-Covers of P. quadridens 

 and its Variety. 



The appearance of the surface of the wing-covers is similar 

 to that of P. bidentatus, but the circular depressions are more 

 numerous. The outer boundary of the excavation is smooth, 

 not hairy: it does not carry tubercles, and it is rounded, not 

 sharp and abrupt. The form described as the type by Eichoff 

 is that in which there is present one large hook similar to the 

 large hook of P. bidentatus, and in addition a small tooth 

 placed lower down than the large hook on the outer edge of 

 the excavation and on the lower third of the outer boundary. 



A varietal form of P. quadridens has been named P. bistriden- 

 tatus, Eichoff, which has, in addition to the projections of 

 P. quadridens, on each wing-cover a small conical tooth placed in 

 the triangular depression. The position of this small tooth is 

 important, it is more distant from the large hook than the 

 corresponding projection in the varietal form of P. bidentatus ; 

 its shape is not that of a hook. The outer boundary of the 

 excavation is similar to that of the varietal form of P. quadridens. 



Relative Frequency of Occurrence of these Forms in Scotland. 

 The four forms described above all occur in Scotland. A list 

 is given below of places in which one or more of the forms have 

 been found. The most common forms are P. quadridens and 

 P. bidentatus var. The bistridentatus variety of P. quadridens 

 is rarer but still not uncommon. The form described as typical 

 P. bidentatus is rare. 



Localities in which Pityogenes Species have been found. 

 Locality. County. 



Murthly. Perthshire. 



Fodderty. Ross-shire. 



Drumshoreland. Linlithgow. 



Kintore. Aberdeenshire. 



Nethybridge. Inverness-shire. 



Attention has been given to the similarities of the beetles of 

 the four forms described. The differences existing between the 

 two species bidentatus and quadridens are not all equally 

 definite. The most definite characters are the nature of the 



