KELLOGG: TAXONOMIC VALUE OF SCALES OF LEPIDOPTERA. 6^ 



large and cylindrical, draws away from the membrane, leaving a 

 space between it and the membrane. In this space the beginnings of 

 scale development appear. In the third stage of wing development 

 the development of scales has fairly begun. In the space above 

 described between the epidermis and the primitive membrane there 

 are at short intervals large spherical cells with large nuclei, and 

 which without exception bear, each, an eiongite process which 

 pushes out between the epidermal cells, and at first appears as a long 

 stalk, which, however, suddenly widens into a more or less spherical 

 bladder. This bladder is the first suggestion of the future scale. 

 At first each bladder is large and irregular in outline. The long stalk 

 is thus somewhat shortened. The free end of the forming scale 

 gradually grows into a point which becomes longer and longer, while 

 the body of the scale and the stalk become shorter, until finally a 

 form is developed which compels recognition of its scale-like char- 

 acter. 



It is a singular circumstance, says Semper, that not all of the scales 

 are developed at the same time, but they develop one after another, 

 so that one can often find the different stages of the scales on one 

 and the same wing. But this disproportion is equalized by the scales 

 growing more slowly in their later stages than in their earlier stages, 

 and Semper noted that the scales attained their complete growth at 

 about the same time. 



Between this stage of scale development and that earlier stage in 

 which the space between the epidermis and the primitive membrane 

 which contains the developing cells of the scales was first apparent, 

 there is a hiatus which Semper's observations were not able to fill. 



In the same manner, says Semper, the development of the hairs of 

 Lepidoptera proceeds, the hairs being completely identical with the 

 scales. Semper observed the development of the antennal hairs of a 

 male Satiii->iia carpini. 'i'hese hairs arise, just as do the scales, from 

 a layer of cylindrical cells. The hairs push out between the cells of 

 the epidermis as do the scales, and the only difference in fact between 

 the scales and these hair.s is merely in the outer form; and this is no 

 real difference, for there may be found between both forms numerous 

 gradatory forms. 



So long as no cuticle is developed by the epidermis the forming 

 scale consists of a fine membrane which is a direct continuation of 

 the parent-cell, and which contains a transparent finely-granular 

 content, v/hich is darkened and contracted by acetic acid. But as 

 soon as the cuticle appears, one sees also developed on the scales 

 and hairs — it was especially ap|iarent on the antennal hairs of Satiir- 

 nia carpini — a thickened layer which where the hair or scale meets 



