134 THE entomologist's record. 



longation (fbr. Ji'dnti.) from its base, which, piercing the grundmem- 

 bran below it, traverses the himen of the wing, pierces the grund- 

 membran of the opposite side, and finally unites with the cuticula of 

 the opposite surface of the wing (fig. 8,/bi-. h'dnii.), and thus every 

 hypodermal cell becomes converted into a long, thin fibre, stretching 

 from the upper to the lower surface of the wing, and the similarity 

 of their appearance to muscular fibres suggests that they may be 

 contractile ; although Mayer believes that they, in time, become ten- 

 dinous cords, serving to hold the opposite membranes of the wing- 

 together during its great expansion, directly after the exclusion from the 

 chrysalis. Schaft'er thought that these fibres were merely the original 

 protoplasmic prolongations (such as are shown in PI. iii., fig. 5, 

 pre.) fused together, but he was quite unaware of the absorption of these 

 prolongations, and the subsequent development of the fibres uniting 

 the opposite membranes forming the wing. 



In the scale itself, the protoplasm which fills the primitive scale 

 undergoes contraction, and becomes coarsely granular, and gradually 

 withdraws from the scale, leaving little chitinous pillars (elm., PI. iii., 

 fig. 11) which bind the upper and lower surfaces of the scale together. 

 Mayer says that the protoplasm is entirely withdrawn, and that the 

 scales then become merely little flattened, hollow, chitinous sacs, con- 

 taining only air. Chapman, however, dissents entirely from this 

 view, and states that no air enters any of the scales until the pigment 

 is fully elaborated. We have ourselves noted that the scales, at this 

 so-called " white " stage, are very different in appearance from the 

 opaque whiteness which characterises actually white scales filled with 

 air, at the final stage of development. It appears that the scales, 

 at this stage, are not filled with air, but are filled with a clear secre- 

 tion from the ha^molymph, containing all the necessary materials for 

 going through the chemical changes which result in pigmentation. 

 The stria tions of the scale may be observed, at this stage, to be due to 

 a series of parallel longitudinal ridges on the upper surface (PI. iii., 

 figs. 10-11), the under surface of the scale is pro\ided Avith but few, and 

 these ill-developed, ridges. 



The next stage of development shows the wings of a yellow-ochre 

 colour, for the secretion from the hsemolymph, which fills the scales, 

 now begins to undergo the chemical changes, which result in pigmen- 

 tation. The formative cells now show great change, and the forma- 

 tion of the scales being completed, and there being no further use 

 for these cells in the economy of the insect, they undergo degenera- 

 tion. At this stage, certain scales (? androconia) situated either upon 

 the nervures or near the outer edges of the wing, have a leucocyte 

 enter them ; the pigmented scales contain no leucocyte. 



The insertion of the scale into the wing membrane is brought 

 about by the filling of the narrow cylindrical stalk of the scale into a 

 minute close-fitting socket, which perforates the wing membrane 

 (PI. iii., fig. 10). It is not set into a tube, as Landois supposed, nor 

 did Mayer discover anything resembling the " Schuppenbalg" de- 

 scribed by Spuler, for the insertion of the scales. 



The transverse folding of the wing membrane is very sharp, and the 

 latter is, in fact, thrown into a very regular series of closely compressed 

 folds {eta. al., PL iii., fig. 10), a single scale being inserted on the 

 crest of each fold. When the imago emerges from the chrysalis, the 



