PEELIMINAEY CLASSIFICATION OF SCOLYTOIDEA. 2 IS 



abdominal segments, spiracles, etc., which are of value in separating 

 the families, but the majority of these characters are of greatest value 

 in connection with the genera and species. 



The egg and embryo doubtless bear some important characters, 

 but they have not been sufficiently studied by the writer to justify 

 their discussion in this connection. 



PHYSIOLOGICAL CHARACTERISTICS. 



A review of the evidence relatmg to the physiological character- 

 istics shows that the feeding, breeding, flight, and social habits, the 

 galleries, larval mmes, host plants, the species of plant, the part of 

 the plant occupied, conditions of the plant, restricted or wide range of 

 host relations, and features in geographical distribution have some- 

 thing to contribute in facts and evidence of more or less taxonomic 

 importance. 



CORRELATION OF MORPHOLOGICAL AND PHYSIOLOGICAL ELEMENTS. 



In order to arrive at satisfactory conclusions in regard to the proper 

 correlation of the mass of taxonomic data mentioned in the foregoing 

 review one must have a far more comprehensive and first-hand 

 knowledge of the subject as applied to the species of the world than is 

 possessed by any investigator at the present time. Therefore it is the 

 object of the writer to call attention to the need of further investi- 

 gation of this broader principle of zoological taxonomy rather than 

 to attempt to draw conclusions. It is evident, however, that at some 

 future time the essential facts will be correlated uito a system which 

 wiU not only indicate true natural relations but perhaps give a better 

 clue to the action of natural laws and a better mterpretation of the 

 fundamental principles involved m the evolution of life in general. 



In order to arrive at sound conclusions the whole subject must be 

 investigated without prejudice for or agamst any theory as to phylo- 

 genetic origin of the organism, or as to the prmiitive or recent char- 

 acter of an organ or element. The problem must be attacked with 

 the view of locating the more important or essential facts relatmg to 

 the distinguishing characters and characteristics as applied to the 

 species and their various aggregations into genera, subfamilies, and 

 families and the major and minor divisions of each. In other words, 

 a given group of organisms should be studied in all of its morphological 

 and physiological aspects with the view of locatmg, b}^ the process of 

 elimination, the elements of primary importance until one or more 

 characters m each of the principal morphological and physiological 

 groups of taxonomic elements are found to correlate in the formation 

 of a harmonious taxonomic compound. 



It has been shown in the foregomg pages that a classification based 

 on any limited set of external or internal elements of the adult body, 



