TAXONOMIC VALUE OF MORPHOLOGICAL CHARACTERS 23 



Pores and Ducts. No thorough investigation of the various wax- 

 secreting glands of the Coccidae and of their ducts and pores has ever 

 been made, yet it is probable that such an investigation would mark one 

 of the most significant steps that can be taken in the study of this group. 

 The existing information is very incomplete and in some instances quite 

 misleading. It is not desirable to enter into any extended discussion of 

 the subject here it is deserving of a monograph by itself but certain 

 facts having a direct bearing upon the particular group under discussion 

 may well be presented. Unfortunately there exists no satisfactory term- 

 inology for the various types of ducts and pores and a certain degree of 

 circumlocution has been necessary in characterizing them, it being unde- 

 sirable to propose a definite terminology until a comprehensive study of 

 the whole subject has been made. 



The wax-secreting glands are of several distinct types, each type 

 discharging its products through the body wall by means of a different 

 type of duct or pore. Certain of these types appear to be common to all 

 the Coccidae, while others are apparently characteristic of particular 

 groups. Their chief value will probably lie in the indications which they 

 give of the relationships of the various genera, although at times they are 

 useful even in the recognition of species. 



The general type of gland opening through a duct (except in the 

 Diaspinae) is shown in text figure 14, which represents a section through 



Fig. 14. Section through a wax gland of Eriococcus adenostomae Ehrh. 



a gland of Eriococcus adenostomae (Ehrhorn). It will be observed that 

 the duct is divided into two parts, a basal part of relatively large diam- 

 eter, the inner end of which is reflexed to form a sort of cup from the 

 rim of which rises the very delicate inner portion of the duct. Modifica- 

 tions of this type are found in the Coccinae and in certain groups of the 

 Dactylopiinae (as this subfamily is understood in the Fernald Catalogue), 



