66 THE SCOLYTID BEETLES. 



SPECIFIC DISTINCTIONS. 



In the literature on Scolytidse, and, for that matter, on almost any 

 group of insects of special systematic and economic importance, there 

 is much confusion, due to different interpretations of specific distinc- 

 tion. Some authors have combined many described species into one, 

 while others have recognized man}^ distinct forms among those here- 

 tofore included in one species, and have proposed as many different 

 names for them. It is evident that whenever ''lumping" or "split- 

 ting" is necessary for the clear definition and recognition of a species 

 it should be done, but it is equally evident that neither should be 

 attempted without an adequate knowledge of at least the genus rep- 

 resented, in order that the true characters of specific distinction may 

 be recognized from those which serve to distinguish the genus or the 

 major and minor divisions of higher rank than the species. 



RANGE OR LIMITS OF SPECIFIC VARIATION. 



The determination of the range or limits of variation in characters 

 utilized for the distinction of a species is one of the most troublesome 

 questions with which the systematist has to deal. With one or a few 

 specimens the line separating one recognized species from another may 

 be distinct and definite, but as the number of specimens from different 

 localities increases the line of distinction from allied forms often 

 becomes less and less distinct until it is almost or quite obscure. 

 Here is where expert judgment, based on experience and a technical 

 knowledge of the special group involved, is required in order to decide 

 whether or not two heretofore recognized and closely allied species 

 should be kept separate or be combined. The recognition of pre- 

 vailing variants or constants, or. of forms having abnormal or normal 

 morphologic and physiologic characters, is of special importance in 

 this connection, as is also the recognition of the disturbing factor of 

 parallel modification in characters and habits among species of the 

 same genus, as well as among those of different genera. 



If the variants connecting two allied groups comprise only a small 

 percentage of the individuals, they may be considered as departures 

 from the constants of the species more nearly represented, and thus 

 the groups so slightly connected will serve the purposes and require- 

 ments of species and neither of them should, in the writer's opinion, 

 be designated as a named subspecies, race, or variety; but if, on the 

 other hand, the connecting variants comprise a large percentage of 

 individuals, and no other characters sufficiently distinct and constant 

 can be found by which individuals may be readily referred to one or 

 the other of the heretofore recognized species, it would indicate that 

 the two are not specifically distinct. 



