TAXONOMIC VALUE OF MORPHOLOGICAL CHARACTERS 



19 



and the character of their vestiture of hairs being minutely dealt with. 

 In general I have not found such characters to be of any special value. 



Fig. 11. Pseudococcus maritimus (Ehrh.) ; outlines of legs, to show variation. 

 A, from Salix at Stanford University; B, from passion flower at Palo Alto; 

 C, from orange in southern California; D, from Mesembryanthemum at La 

 Jolla ; E, from roots of clover at Medford, Oregon. 



In text figure 11 are shown some of the variations in size found in P. 

 maritimus. Where extreme differences are found, such as in the case of 

 Erinm lichtensioides and Ripersiella kelloggi where the legs are much 

 reduced in size, they may be of a certain value. Reference to the legs 

 has been omitted in this paper except in such cases. 



Fig. 12. Tarsal claws of : A, typical Phenacoccus, and B, typical Pseudococcus. 



The tarsal claw, however, affords certain very convenient generic 

 characters. In certain groups there is a minute tooth or "denticle" on 

 the face of the claw (figure 12) which affords a most valuable "key 

 character." Taken by itself this character is probably of little importance, 

 for it has certainly been independently developed in widely separated 

 groups (for instance, it appears in some of the Margarodinae), but in 

 conjunction with other characters it is extremely useful. I have not been 

 convinced that the digitules merit special attention. 



