New York Agricultural Experiment Station. 305 



the molted skins showing through the scale. In many cases the 

 nipple is near the margin as shown at Plate XLIX, Fig. 1. The 

 two large scales in this picture are adult females. The first molt 

 causes the whole central area of the scale to appear a lighter 

 shade than the remainder. The white cottony mass, which is 

 forced beyond the edges of the scale turns dark, forming a dark 

 ring. The second molt forms a lighter area, which, as it shows 

 only toward the edge, the scale now being much thinner at the 

 edges than toward the apex, forms a lighter ring. Thus there 

 are two more or less distinct broad light bands with a narrow 

 dark band between. Plate XLVIII, Fig. 7. At Plate XLVIII, 

 Fig. 8, a mature scale is shown turned back exposing the living 

 insect. The dark area forming the posterior extremity of the 

 insect's body is the anal plate. It is by means of the microscopic 

 characters of this plate that the species may be definitely deter- 

 mined. Plate L, Fig. 1 is from a photomicrograph of the anal 

 plate of the San Jqs6 scale, and Fig. 2 of Aspidiotus oestreceformis, 

 a species common in this State that is sometimes mistaken for it. 



While the above description of scale formation is fairly typical, 

 there is much variation. In this connection the following notes 

 giving the details of the formation of the scales of a number of 

 individuals kept under the same conditions may be of interest. 

 All of the larvae were placed on smooth-skinned apples and kept 

 in the laboratory or insectary. 



No. 1. — Ten larvie born September 4. By September 8 they 

 TV'ere completely covered by the white cottony secretion. On this 

 date the cottony mass was removed, but by September 10 it was 

 replaced by another covering of waxy filaments which were more 

 closely matted together than the former. The scales were white 

 like the first and on this date showed a faint indication of a cen- 

 tral nipple but no ring about the nipple. By the following day a 

 slight ring-like depression had formed about the nipple. Until 

 September 19 there was no apparent change but on that date 

 the scales appeared to be turning darker in color. By September 

 21 they had begun to turn very dark, nearly black on the outer 

 20 



