242 THE COCCIDAE 



shown in all in the modification of the pygidium and the pygidial 

 fringe. The generalized pygidium contains five distinct groups 

 of genacerores, at least three pairs of lobes, and two or three 

 broad distapectinae in each incisura and several on each lateris. 

 The line of modification is a transformation of the pectinae into 

 plates, a reduction in the number of plates, a reduction in the 

 size of the lobes, and finally in the number of lobes. The modi- 

 fication proceeds always along each side of the pygidium from 

 the cephalic end to the meson or caudal end. With the reduction 

 in the pygidial fringe there proceeds also a reduction in the num- 

 ber of eerores in the groups of genacerores and finally their com- 

 plete loss. One of the highest types of specialization is repre- 

 sented by a few species where lobes, plates, pectinae, and gena- 

 cerores are wanting and the projections of the pygidium are 

 limited to latadentes. Whether there is an acceleration of the 

 development and in the last named species the pygidial fringe is 

 to be found only in the pygidium of the second nymphal stage 

 is not known. But representing the highest type of specializa- 

 tion in each of the four tribes first named are genera in which 

 the adult female shrinks away from the last or second nj'mphal 

 skin but never escapes from it. The young are born alive and 

 escape through openings in the cuticle, that is the second exuvia 

 or puparium as it is designated in such species. The pygidium 

 of the adult female may be entirely without projections or bear 

 a large number, none of which are homologous with any part of 

 the pygidial fringe. These projections, the pseudolobes, are fre- 

 quently asymmetrical. There has been an acceleration in the de- 

 velopment of the pygidial fringe and it is frequently found in 

 the pygidium of the second nymphal stage, but in certain spi'cies 

 the pygidial fringe is Avanting even in the second nymphal stage 

 and is to be found only in the pygidium of the first nymphal 

 stage. The species transforming in a puparium represent the 

 highest type of modification and specialization. 



The expression in the following table, of the adult female or 

 of the second nymphal female, does not imply that both of these 

 stages in all species must be examined before the position of any 

 given species can be determined. It sliould not be forgotten that 

 the characters of the pygidium of the second nymplial female can 

 be secured at all times by mounting the second exuvia of the 

 .scale. It does mean, that, if the structure named is wanting in the 

 adult female, the pygidium of the second nymphal fiMuale should 

 be examined to determine whether it is present or absent in this 



