TAXONOMIC VALUE OF MORPHOLOGICAL CHARACTERS 21 



tion of these globules, at the most four in number, corresponds to the 

 position of the dorsal ostioles and there seems to be no room for doubt 

 that it is from these ostioles that they arise. Whether they are secretions 

 from special glands or are of some other origin, I cannot at present say. 

 The connection of these globules with the dorsal ostioles has been noted 

 by Comstock in his Report of 1882. 



In some cases the anterior pair of these ostioles appear to be much 

 reduced in size and they are usually somewhat difficult to see, due to the 

 fact that they lie directly above the anterior legs and are thus more or 

 less obscured in preparations. For this reason I am not prepared to say 

 that this pair is always present, but the posterior pair is to be found in 

 all the Pseudococcine forms that I have seen. I have not been able to 

 find them in the members of any other group and therefore regard them 

 as perhaps the most distinctive character of the group here under con- 

 sideration. 



Cerarii. This term seems first to have been used by Smith (9b, 

 p. 74) f to designate the marginal groups of pores and differentiated 

 spines (the "lateral patches of bristles" of some authors) from which 

 arise the tassels or "filaments" of wax that are such striking features of 

 many species of mealy bugs. While vague references to these structures 

 have been made by various authors, Berlese (1, p. 81) seems to have 

 been the first to describe them at any length, while Marchal (7) has 

 been the first to realize their taxonomic value. Smith (9b), who seems 

 not to have been familiar with Marchal's paper, has independently con- 

 cluded that "the cerari as specific characters are very promising," and 

 Brain (2) and Hollinger (6) have made some slight use of them. 



These are to be regarded as structures of the very highest taxonomic 

 value. They appear to be found only in the Pseudococcine group, al- 

 though not all of the species belonging to this group possess them. This, 

 together with the fact that they are sometimes so much modified as to 

 render them scarcely recognizable, reduces their value as a group char- 

 acteristic, but they still remain serviceable for generic and specific differ- 

 entiation. 



A typical cerarius consists of a pair of spines (herein spoken of as 

 the "cerarian spines"), set close together at the margin of the body and 

 usually accompanied by a more or less distinct group of triangular pores 



tThe derivation of this word is not explained by Smith and he has used the 

 spelling "cerari" in both singular and plural. I am informed by Professor Elmore 

 of the Department of Latin of Stanford University that the word appears to be 

 incorrectly formed. He suggests that the spelling "cerarius" for the singular and 

 "cerarii" for the plural be adopted, with "cerarian" for the adjective form. I have 

 therefore used these forms throughout this paper. 



