HOMOPTERA 



447 



Thus, for example, the cerores that occur in four or five groups about 

 the genital opening in many of the Diaspidinas (Fig. 52 1 , g) are termed 

 genacerores. 



The features of the pygidium. — The pygidia of adult female diaspids 

 present characters that are much used in distinguishing the species 

 of this subfamily; among these are the following. 





Fig. 522. — A composite diagram of a pygidium: a, anus; b, marginal ceratubae, 

 with elongated openings; d, ceratubae opening through plates; e, linear 

 ceratubae; /, /, /, lobes; the lobes of the second and third pairs are divided. 



The position of the anus, which opens on the dorsal aspect of the 

 pygidium at varying distances from the end of the body (Fig. 522, a). 



The opening of the vagina, on the ventral aspect of the pygidium 

 (Fig. 521, v). 



The presence or absence of groups of genacerores (Fig. 521, g), the 

 number of these groups when present, and the number of cerores in 

 each group. The different groups are distinguished as the median 

 group {me so genacerores), the cephalo-lateral groups, one on each side 

 (pregnacerores) , and the caudo-lateral groups, one on each side 

 (postgenacerores) , respectively. These all open on the ventral aspect 

 of the pygidium. Each genaceroris has several openings. 



The position and number of openings of ceratubas, and the types 

 of ceratubas that are present (Fig. 522). 



The number of pairs of lobes borne by the margin, the shape of 

 the lobes, and whether they are divided or not (Fig. 522, /, /, /). The 

 pairs of lobes are numbered, beginning with the pair at the end of 

 the body; in some species this pair is represented by a single lobe. 



The number of pairs of incisions (incisures) in the margin of the 

 pygidium (Fig. 521, i). 



The presence or absence of thickenings of the margins of the 

 incisions (densarice); these are thickenings of the ventral wall (Fig. 

 521, d). 



