TAXONOMIC VALUE OF MORPHOLOGICAL CHAR- 

 ACTERS, SECRETIONS, AND BIOLOGY 



MORPHOLOGY 



The morphology of the mealy bugs has been dealt with to some 

 extent by Berlese ( 1 ) who has described some of the structures that are 

 available for taxonomic purposes, although he has not himself carried out 

 any taxonomic studies; Marchal (7) seems to have been the first to 

 make use of these characters. Smith (9a) has investigated the value of 

 the characters ordinarily employed and in a later paper (9b) has dis- 

 cussed the possible value of others. Brain (2) has also pointed out the 

 possible value of many characters not ordinarily employed, although, curi- 

 ously enough, he does not himself make any particular use of these char- 

 acters. In no case does there seem to have been any real appreciation of 

 the full value of the characters observed and there still remain some that 

 do not appear to have been noted at all. 



In view of the fact that no wholly satisfactory discussion of the tax- 

 onomic value of the various morphological features of this group exists 

 it is necessary to consider the matter at some length. Unfortunately the 

 material available for study is somewhat limited and most of the conclu- 

 sions presented must be regarded as but tentative. However, they apply 

 to the material examined by me (which includes a number of species not 

 coming within the scope of this paper), and very probably apply to a 

 considerable degree to the remainder of the group. 



Adult Female 



Antennae. Almost since the serious study of the Coccidae began the 

 antennae have been relied upon to furnish both generic and specific cri- 

 teria. The present generic concepts in the group here under consideration 

 are based in large part upon the number of segments in the antennae of 

 the adult female and the relative or actual lengths of the individual seg- 

 ments have been much used for purposes of specific differentiation. The 

 value of the antennae in defining generic groups will be discussed in a 

 later paragraph on generic concepts and we shall here consider merely 

 their value as specific criteria. 



If we compare a limited number of individuals of a few species it 

 may not only appear that there are certain rather obvious differences in 

 the actual lengths of the individual segments and of the antennae as a 

 whole, but there may also be differences in the relative lengths of the 



