192 THE SCOLYTID BEETLES. 



In the family Scolytidae there appears to be a wide range of varia- 

 tion. In ErineopMlus schwarzi Hopk., of the subfamily Hexacol- 

 inse, the rod is absent, the valve present, and the femora are long 

 and slender. In some species of the genus Scolytus the body is 

 greatly modified, somewhat resembling a seminal rod. The valve 

 is absent and the femora are rudimentary in S. muticus Say and 

 S. quadrispinosus Say (fig. 109). In S. rugulosus Ratz., however, 

 (fig. 108) the femora are long, the valve is represented, and there are 

 some additional parts; in fact, all of the elements are radically differ- 

 ent from those of the other two species. 



In one genus and one species of Scolytoplatypodidag the rod is 

 absent and the femora are large and very broad, differing in this 

 respect from anything yet observed in the entire superfamily. 



In two genera and five species of the subfamily Platypodinse the 

 body is long and slender, but without the spicule, end plates, seminal 

 valve, or rod, and the femora are represented by short hooks at the 

 basal angles of the body. The tegmen is present in the form of a fork. 



A study of the available data relating to the primary and secondary 

 elements of the male organs of reproduction shows that within the 

 families, subfamilies, and genera there is a very wide range of varia- 

 tion and that the same or similar elements individually, or in various 

 combinations, are often paralleled in soecies of widely separated 

 genera and subfamilies, so that their principal taxonomic value 

 appears to be restricted to the separation of species and minor divi- 

 sions of the genus. 



It appears that if there is any line of progressive modification 

 within the major and minor groups, it is from a simple form without 

 seminal valve, seminal rod, or end plates, as in some of the Crypha- 

 linse and in the Platypodinse, to the most complex forms with or 

 without the valve and with or without the rod, the rod reaching its 

 highest development in Xylehorus, Dryoccetes, Lymantor, Ips, and 

 allied genera; while the valve without the rod reaches its highest, 

 development in Hylesinus and allied genera in the Hylesininae. 



Terminology op the Reproductive Organs. 



In the following list it is intended that the numbers and letters 

 should serve to designate the elements of the reproductive organs 

 rather than names, because the names proposed by different authors, 

 including the writer, do not agree in all cases in designation or 

 interpretation. 



Male Reproductive Organs. 



(Figs. 101-110.) 



Division 1. Posterior chitinous division. 



Division 2. Posterior membranous division. 



Division 3. Median division. y 



Di\asion 4. Anterior division. 



