300 THE COCCIDAE 



which there are two. The word Uiaspis would mean literally 

 then two siiields and since the genus is the typical one of the 

 tribe, the eonnuon name of The Double-shielded Scales has been 

 applied to them. Tlie name of a subfamily and tribe according 

 to rule is derived from the stem of the genative which in the 

 case of Diaspis is Diaspidis, hence, the proper form for the 

 names of these groups is Diaspidinae and Diaspidini and not 

 Diaspinae and Diaspini as they are generally written. 



The body like the scale varies considerably in size. Where 

 the scale is pyriform, mussel-shaped, or elongate, the body if 

 elongate, is usually two to four times as long as broad ; but in 

 those species with a circular scale, the body is shorter and broader 

 and the greatest width is through the thoracic region which is 

 always much wider than the preabdomen. In dried specimens 

 the segments of the preabdomen are crescentic and retracted into 

 the caudal part of the thorax. The pygidium in turn is retract- 

 ed into the caudal end of the preabdomen so that the preabdomen 

 and the pygidium seem to constitute only a small portion of the 

 area of the body. The cephalic part of each lateral margin of 

 the thorax sometimes bears a short bluntly rounded tubercle. In 

 those species with elongate bodies the preabdomen and pygidium 

 are larger and constitute, even in dried retracted individuals, a 

 much larger and more prominent portion of the body. The ce- 

 phalic end of the body is usually broad and convexly rounded. 

 The width of the cephalic end varies with the species, in some it 

 is the broadest part of the body while in others it may be only 

 one-half or less of the greatest width. The body, while it is al- 

 ways depressed, is never decidedly flattened as in some other 

 tribes of Diaspidinae. The antennae are usually represented by 

 minute distant tubercles bearing one to three stout setae. 



The preabdomen is generally distinctly segmented and easily 

 distinguished from the thorax and pygidium. The segments are 

 separated by deep constrictions marking the position of the coriae. 

 The portions of the segments between the coriae are generally 

 strongly convex, which generally emphasizes the depth of the 

 coriae. The lateral margins of the segments, particularly the 

 caudal ones, are frequently provided with plates or short blunt 

 plate-like projections, but never with bracteae. 



The pygidium is comparatively large and well differentiated. 

 It is usually circular or oval in outline, both the cephalic and the 



