TRIBE ASPIDIOTINI 381 



as the San Jose Scale, belong to this tribe. The general form of 

 the scale and of the body makes it an easily identified group and, 

 since there is but slight variation in their general structure, there 

 is but slight reason for misplacing the species of this tribe in any 

 systematic scheme. The species show a wide range of variation 

 in many of the characters peculiar to them. This is particularly 

 true when they are compared as to the serial modification of their 

 lobes, pectinae, plates, genacerores, transformation in a puparium, 

 and the development of pseudolobes. Because of this range of 

 variation, the tribe includes several very generalized species and a 

 number of greatly modified and highly specialized species repre- 

 senting a number of distinct lines of development. 



The scale of the adult female is quite constant in form. It is 

 circular in outline and usually varies from this shape only in those 

 individuals that occur on narrow leaved plants or where the space 

 for development of the scale is limited either through the crowding 

 together of the insects upon the plant or the form of the plant. 

 In a few other species, apparently without cause, certain individ- 

 uals also depart from the typical circular form of the scale. The 

 scales of such individuals are usually short oval in outline, very 

 rarely twice as long as wide. They are readily differentiated from 

 the round or oval scales of other tribes in that the two ends of the 

 scale, if oval, are similar and broadly rounded, while the two 

 exuviae are always placed near the center of the scale, very rarely 

 if ever adjacent to the periphery of the scale and never projecting 

 over the margin. They differ also in that the first exuvia is borne 

 superimposed over the middle of the second and not at one end as 

 in the scales of the other tribes. In individuals of this tribe the 

 nymphs of the first stage when ready to cast their cuticle or molt, 

 rupture it around the periphery of the entire body and the 

 antennae remain attached to the ventral portion of the exuvia and 

 not to the dorsal portion as in the scales of the previously described 

 tribes. The wax of the scales is generally of considerable extent 

 and while ordinarily dark in color, brownish, reddish, or blackish, 

 they are often grayish, and only rarely are whitish or white. The 

 waxy covering may be either thick and opaque or thin and trans- 

 parent. The first exuvia is usually covered by a very thin cover- 

 ing of wax and in many species frequently bears a minute central 

 nipple-like prominence of wax, the cicatrix, which is the remains 

 of the first downy ball of wax formed by the nymph of the first 

 stage. The cicatrix is white in color and when placed upon a dark 

 colored exuvia is very conspicuous. The exuviae are generally 



