SYSTEMATIC TREATMENT 31 



ent, while in both species the ducts are distinctly of the Eriococcine type. 

 Certain other genera remain to be elucidated before their position can 

 be determined. 



GENERIC CONCEPTS 



As I have stated in an earlier paragraph the present generic con- 

 cepts in this group are based largely upon the number of segments in 

 the antennae of the adult females. The splendid simplicity of this 

 arrangement is indeed attractive. We need only name a genus to corre- 

 spond with each different number of antennal segments, with perhaps a 

 few others for the reception of "aberrant" forms, and the system is com- 

 plete. This is in fact practically what has been done. However, the 

 unnatural character of the groups thus obtained has in part been recog- 

 nized and the system has not been strictly adhered to, with the result 

 that its simplicity has been somewhat marred. The genus Ripersia was 

 originally established for the reception of forms with six-segmented an- 

 tennae, but the majority of the species now referred to it have seven. 

 Pseudococcus was intended for forms with eight-segmented antennae, 

 but it now includes species with seven segments as well. As a conse- 

 quence of this it appears that in several instances a species has been 

 referred to one genus or another simply because "it looks like a Ripersia'' 

 or a Pseudococcus as the case may be. 



I have attempted in the present paper to utilize other characters than 

 the antennae for the recognition of generic groups. For this purpose 

 the cerarii have seemed most useful, the number of pairs present being 

 considered as diagnostic. It must be admitted that the groupings thus 

 obtained are not entirely satisfactory, even with as few species as are 

 here considered. It is not at all improbable that a reduction in the num- 

 ber of pairs of cerarii might occur in groups that are but little related, 

 and in fact this appears to have happened. Nevertheless at its worst a 

 system based fundamentally upon this character is much more satisfying 

 than one based upon the antennae, and when supplemented by the other 

 characters that are available seems to approximate a natural arrangement. 



I wish specifically to disclaim any attempt to limit or define the 

 genera here dealt with except as they concern the limited fauna discussed. 

 The number of species available to me for examination is sufficient 

 merely to indicate something of the difficulties that must be overcome 

 before any final definitions can be formed. The task is one for a student 

 who has before him a very large proportion of the known species and 

 must not be undertaken on the basis of any purely local fauna. 



