26 Diaspinc?. 



coating secreted during the previous stage. It is at this time, 

 before the further enlargement of the scale, that impregnation 

 takes place. The fecundated female soon outgrows its former 

 covering, which is accordingly supplemented by the further forma- 

 tion of the membrane-like secretion mentioned above. This 

 supplementary part may be of stouter or finer texture, opaque or 

 semi-transparent, colourless or coloured, according to the species ; 

 but it is produced in practically the same way from special tubular 

 organs or spinnerets, situated chiefly on the margins and dorsal 

 surface of the terminal segment or pygidium. In this later stage 

 the extension of the puparium is continued until it is of sufficient 

 size not only to protect the soft-bodied insect itself, but to form a 

 receptacle for the numerous eggs that are now deposited there. 

 The so-called ventral scale is really continuous with the upper 

 part, and forms a bed upon which the insect rests ; but this part is 

 usually very much thinner, often consisting merely of a delicate 

 film adhering closely to the surface of the plant, though occasionally 

 it is of almost as firm a texture as the upper part. 



In some genera, such as Aspidiottis and Diaspis, the secretionary 

 supplement completely surrounds the pellicles {pi. I. Jigs. 7, 4); in 

 others, such as Mytilaspis or Chioiiaspis, it is extended in a back- 

 ward direction only {pi. I. Jigs. 5, i). In the former case, the insect 

 must revolve completely around the point of attachment during 

 the construction of the puparium. In the genera forming elongate 

 puparia, a to-and-fro sweeping motion of the hinder parts of the 

 body is sufficient to produce the resulting form of scale. 



The abnormal genera Aonidia and Fiorinia have a slightly 

 different development. In these the insect attains its greatest 

 dimensions during the second stage. At the time of the- second 

 moult the skin is not actually shed, nor is it even ruptured, but 

 completely encloses the body of the adult female, which becomes 

 gradually reduced in size and shrinks away from its former skin, 

 the vacant space, in the case of Fiorinia, being subsequently packed 

 with the ova. It is remarkable that, although the skin of the 

 enlarged second pellicle is entire in these two genera, the rostral 

 apparatus is still displaced to the posterior extremity, indicating 

 a most extraordinary distension of the skin of the anterior parts. 



In some species the puparia have the appearance of being 

 situate beneath the cuticle of the plant ; but this is seldom really 

 the case, the effect being produced by the presence in the scale 

 of hairs or loose fibrous matter superficial to the actual cuticle. 



