214 THE SCOLYTID BEETLES. 



such as those found m the proventriculus or in the male or female 

 organs, will suggest a phylogenetic system, but when it is found 

 that each systern differs from the other to such an extent that the 

 same genus or species will occupy a radically different position in 

 the different systems it is perfectly plain that the true taxonomic 

 value of the elements has not been correctly interpreted or applied. 

 On the other hand, it is equally plain that if characters can be found 

 m all or a majority of the groups of external and internal elements 

 which point in the same direction, we may safely assume that we 

 have more nearly approached the true principle involved and the 

 ideal classification. 



Examples of an attempt by the writer to correlate and harmonize 

 the various morphological and physiological elements wlQ be found 

 in the synoptic tables of Dendrodonus, Part I of this bulletin, and of 

 Pissodes in Technical Series 20, Part I. 



PARALLEL MODIFICATIONS. 



Parallel modification in morphological and physiological elements 

 is without doubt an important factor to be considered in taxonomy. 

 It is evident from a comparative study of the various systems of 

 classification that the failure of taxonomists fuUy to realize its im- 

 portance has in many cases led to wrong conclusions. It has been 

 shown in the foregomg discussion that there are a great many ex- 

 amples of parallel characters and characteristics in widely separated 

 species and genera and that if they are not recognized and properly 

 interpreted as .such by the taxonomist, radically wrong positions 

 will be assigned to many species and genera. 



REVERSALS. 



The reversal of characters and characteristics in different species 

 of the same genus or in different genera and larger groups is another 

 important fact to be kept in mind, especially as related to secondary 

 sexual characters. Therefore it is never safe to conclude that be- 

 cause a given character or a group of characters is of special value 

 in distinguishing one group, genus, species, or sex, it will hold in all 

 cases. There have been numerous examples of wrong determina- 

 tion of the sexes from a failure to recognize this principle, as has been 

 pointed out by the writer (Hopkins, 1894, pp. 274-280) and Bland- 

 ford (1895, pp. 83-86). As has been shown on preceding pages, 

 reversals are also found m specific, generic, and group characters, 

 even to the subdivision of the superfamily, where we find a most 

 striking example in the reversal of the apical spine or process of the 

 anterior tibia from the inner to the outer angle. 



