SUBFAMILY DIASPIDINAE 219 



which is formed by the fusion of four others, is known as the 

 pygidium. The abdomen, therefore, consists of nine segments. 

 The five preabdominal segments are distinct in Lepidosaphes, but 

 in Chionaspis and some other genera, the fifth preabdominal 

 segment is combined with the pygidium, so that in such genera 

 there are apparently four segments in the preabdomen and five in 

 the pygidium. The margin of the pygidium and of the abdominal 

 segments usually bears projections, but they are quite different in 

 form from those found in the adult and described later. The 

 caudal portion on each side of the meson bears a large prominent 

 seta, an anal seta, which is one-half or more the length of the 

 body. The first stage nymphs of certain genera show structures 

 that may be anal lobes, but they are never distinct. The anal 

 ring and anal ring setae are never present. The anus, a circular 

 opening located on the dorsal aspect of the pygidium, is always 

 distinct. 



The first nymphal stage is a comparatively short one. There 

 is considerable variation among the different genera in the way 

 in which the cuticle is molted at this time. In the genera Diaspis, 

 Lepidosaphes, and their allies the old cuticle is ruptured trans- 

 versely between the points of attachment of the antennae and the 

 rostrum. The cuticle is then ruptured along each lateral margin 

 to the pygidium and the ventral portion of the cast skin or exuvia 

 is rolled caudad and comes to rest upon the pygidium. This 

 explains why the mouth-parts are located over the pygidium in 

 certain mounted individuals, a condition that nonpluses many 

 beginners. This method of dividing the exuvia separates the 

 antennae which remain attached to the cephalic portion of the 

 dorsal exuvia and project horn-like beyond its cephalic margin, 

 even in old dried exuviae, while the caudal portion of the ventral 

 exuvia is folded upon the pj-gidium. In the genus Aspidiotus and 

 its allies the split extends entirely around the margin of the body 

 and the entire dorsal aspect is separated from the ventral, forming 

 two distinct plates, a dorsal exuvia and a ventral exuvia. The 

 dorsal plate in this case always lacks the dried porrect antennae. 

 The dorsal exuvia forms a part of the dorsal scale and the ventral 

 exuvia forms a part of the ventral scale, but is frequently lost. 



The female nymphs at the first molt lose their antennae and 

 legs, become greatly enlarged in size, and are more like the adult 

 in general form. This is also true of the structures on the margin 

 of the pygidium. The second stage females may live for a con- 



