28 SCALE INSECTS OF SANTA CRUZ PENINSULA 



Kermes rattani Ehrh. 

 Fig. 9A. 



Originally described from Quercus chry sole pis in this locality. 



I have been able to obtain only fully mature individuals of this species 

 and can say nothing as to its morphology. In appearance the species 

 presents a wide range of variation both in form and coloring. The typi- 

 cal form is practically spherical, but various distortions arise because of 

 unfavorable position. 



Judging from the figure of Rermes mirabilis King and from the fact 

 that its type locality is the same as that of K. rattani this species may quite 

 safely be regarded as identical with K. rattani. Mr. Ehrhorn concurs in 

 this opinion also. 



Genus PSEUDOCOCCUS Westwood. 



In an earlier paper x I have dealt at some length with this and related 

 genera. More material is now available than at thje time when this 

 paper was published, and certain conclusions there expressed require 

 modification. In addition certain errors, both of observation and judg- 

 ment, may be corrected. 



In this earlier paper the genera Phenacoccus and Pseudococcus were 

 in part separated by ascribing eighteen pairs of cerarii to the former 

 genus and seventeen to the latter. A re-examination of my material in- 

 dicates a serious error in observation. In Pseudococcus citri and P. 

 kraunhiae there are in fact eighteen pairs, although P. longispinus and 

 some other species have but seventeen. This character, therefore, cannot 

 be relied upon for the separation of these genera. Neither may the num- 

 ber of antennal segments be considered as decisive, since there are some 

 species, notably Phenacoccus solani Ferris, in which the antennae may be 

 either eight- or nine-segmented. Nor is the single remaining character, 

 that of the presence of a denticle on the claw in Phenacoccus, entirely 

 satisfactory, as this denticle is at times so extremely small as practically 

 to be obsolete. 



I am by no means prepared to concede that these two genera should 

 be united, for their types are certainly sufficiently different, and it is 

 probable that a large majority of species may be placed satisfactorily. 

 Neither am I prepared to say just where the division between the two 

 genera should come. This particular difficulty is but one of a series 

 of difficulties that arise in dealing with this group, as I have elsewhere 

 pointed out. 2 The difficulties may not be disposed of without the exami- 

 nation of a much larger series of forms than have yet been studied. 



1 "The California Species of Mealy Bugs." Stanford University Publications, 

 University Series. 1915. 



2 "Contribution to the Knowledge of the Coccidae of Southwestern United 

 States," p. 31. Stanford University Publications, University Series. 1919. 



