238 THE COCCIDAE 



of the primary groups. This latter method may have been the 

 original method of formation and the appearance in the sjjecies 

 named may be due to a reduction in the number of cerores and 

 their later migration and isolation. 



The number of cerores in each group varies greatly. Tliere 

 may be only a few, as one, two, or three, or there may be forty or 

 more. This variation in the number of cerores, unfortunately 

 is not fixed even within specific limits, but the comparative num- 

 ber in a group is often of value in separating species or groups 

 of species. 



Each genaceroris is a disk-shaped ceroris with several irreg- 

 ularly arranged comparatively large openings. The fact that 

 they are present only in the adult is of value in those species 

 possessing them in deciding whether a given individual is an 

 adult or a second stage female nymph. The genacerores were 

 originally considered as forming a considerable part of the scale 

 and because of this belief tliej' were named spinnerets. They 

 excrete a fine powdery wax which is mixed with the eggs as they 

 are extruded. Green has called attention to the fact that most 

 of the species provided with genacerores lay eggs, while those 

 species without these structures give birth to living young. 

 Those species provided with genacerores and giving birth to liv- 

 ing young possess only a very few cerores in each group. The 

 genacerores are similar in structure to the spiracerores, but in 

 certain species have a fewer number of openings than the gena- 

 cerores. The fact that the genacerores are present only in the 

 adult female and their location about the vulva would suggest 

 that they must be homologous with the cerores peculiar to other 

 adult females, certain eriococcids, and from which the wax for 

 covering the eggs is excreted. 



Each female and male of the Diaspidinae is covered by a thin 

 sheet or pellicle known as a scale. It is frequently incorrectly 

 designated as a puparium. This term should be applied only 

 to the last nymphal exuvia in which the adult female of certain 

 coccids, as the females of the genus Aonidia, pass their life and 

 the last larval cuticle or exuvia in which the pupae of certain 

 Coleoptera and Diptera complete their pupal life. The scale is 

 composed of three distinct products, the molted skins or cuticle 

 of the first and second nymphal stages in the female and the first 

 in the male, a mass of threads of wax which are poured from the 

 oraceratubae and fuse upon coming into contact with each other, 

 and according to Berlese to a mass of excretion formed by the 



