OF LEPTDOPTEROUS INSECTS. S03 



under and nearly pellucid layer of the scale uninjured, and 

 without the slightest vestige or even impression of the striae; 

 thus proving, in the most satisfactory manner, the existence of 

 three distinct layers : for had the upper and coloured layer, as 

 I at first suspected to be the case in the scale of M. Menelaus, 

 been merely a thin membrane connecting the striae, it could 

 not possibly have been removed from, comparatively speaking, 

 so large a surface, without disturbing them to a considerable 

 extent. In numerous other instances, also, I observed that 

 the upper coloured layer was partially removed, without at all 

 injuring or disarranging (he striee beneath. Having thus 

 satisfied myself with regard to the structure of this portion of 

 the scale, I next endeavoured to ascertain whether the striae 

 were merely solid cartilaginous filaments, for the purpose of 

 giving additional strength to these thin and beautiful tissues, 

 or whether it was probable that they were a series of minute 

 tubes, similar in their structure and purposes to the canals, 

 which serve the double oflSce of giving strength to, and, at the 

 same time, conveying the blood through the wings of Hemi- 

 pterous and other similarly constructed insects. 



In this investigation, let me assure the reader, that the 

 observer has infinitely greater difficulties to encounter than he 

 has in merely ascertaining the existence of distinct coats or 

 layers in the scale, and it will convey some idea of the nature 

 of these difficulties, when I state, that upon carefully measuring 

 one of the dark-brown scales from the wing of Papilio Paris, 

 I found that its greatest breadth was but ,^ of an mch. The 

 quill by which it had been attached to the wing was —„ of an 

 inch in diameter ; the distance of the striae from each other, 

 i^^i of an inch ; and the diameter of the longitudinal strise 

 themselves, ~ of an inch. 



It is usually the case, that the whole surface of the scales, 

 from the wings of Lepidopterous insects, appears covered by 

 numerous parallel striae, running in a longitudinal direction, 

 with occasionally shorter ones at right angles, which connect 

 the longer ones with each other. These when viewed with a 

 power of 1000 linear, exhibit precisely the same appearance as 

 the well-known canals in the wings of Chri/sopa perla, and 

 other such insects. The junctions between the larger and the 

 smaller striae upon the scales, present the same appearances as 

 the junctions between the larger and the smaller canals in these 



