184 



THE SCOLYTID BEETLES, 



There is a wide range of variation in the proventricular plates and 

 their armatures, such as the various divided and undivided forms 

 with and without the "brush'' of fine masticatory teeth. These 

 variable forms appear to be of considerable taxonomic importance 

 when correlated A\ath other internal and external characters. 



The classification proposed by Lindemann and Niisslin, as based 

 on the structural characters of the proventricular plates, with a few 

 plainly evident exceptions, correlates in a striking manner with the 

 external characters adopted by the writer for the major and minor 

 groups of genera. When the principle of parallel modification is 

 considered, the genera which seem to be out of place in the classifi- 



.Vf 



Fig. 101. — Dendroctonus valens: Mem- 

 branous and nonchitinous elements of 

 the male reproductive organs. See ter- 

 minology under Divisions 2, 3, 4, pp. 

 192-193. (Original.) 



Fig. 102. — Xyleborus saxeseni: Chitinous ele- 

 ments of male reproductive organs. See ter- 

 minology, Division 1, pp. 192-193. (Original.) 



cations based on proventricular characters alone will, when correlated 

 with a combination of characters, fall into their natural positions. 



REPRODUCTIVE ORGANS. 



The Reproductive Organs of the Male. 



The reproductive organs of the male (figs. 101-110) have been 

 studied and figured by several investigators as follows: 



Table V. — Summary of previous studies of the male reproductive organs by various authors. 



Number 

 of genera 

 repre- 

 sented. 



Lindemann 



Verhoefl 



Fuchs 



Niisslin 



Fuchs 



Sharp 



Year of 



Number 



publi- 



of species 



cation. 



figured. 



1875 



32 



1896 



3 



1911 



20 



1912 



24 



1912 



30 



1912 



2 



