T. F. SMITH ON THE FINER STRUCTURE OF BUTTERFLY SCALES. 179 



It is pretty well known that most insect scales are formed by 

 two membranes, sometimes plain and sometimes corrugated, and 

 that in the Lepisma the two corrugated membranes cross each other 

 at an angle, giving it the appearance of spines. In addition to 

 that there are very fine cross-ribbings, the same as on most butter- 

 fly scales, but except in some of the smaller scales are nearly all 

 torn and hang about in all directions. If you imagine a lady's 

 antimacassar with long, plain bands from end to end, and most 

 of the cross stitches between them torn, you will have the ap- 

 pearance presented by one of the membranes of the Lepisma scale. 

 The other corrugated membrane crosses this one at an oblique 

 angle, and where any part of the fine cross-ribbings cross the 

 oblique markings there is the appearance of beads. Dr. Pigott 

 claimed these beads as a proof of the advancing definition of 

 object glasses, and within certain limits he was right, but it re- 

 quired the definition of the oil immersion to complete the evidence. 



But while there is a boldness in asserting the presence of a 

 certain structure on imperfect evidence, there is also a boldness of 

 denial, and this is exemplified in a paper read before the Royal 

 Microscopical Society in about 1874, by Mr. Mclntire, on butterfly 

 scales, in which he correctly figures the beading or villi, but calls 

 it pseudo-beading. I am afraid, however, it cannot be explained 

 in this manner, as microscopical ghosts will rise from anywhere 

 they are conjured up, but on butterfly or moths scales will rise 

 from one side only, proving to me that they have a real presence. 

 This small beading will rise on the surface of nearlv all the scales 

 I have examined, but it is impossible to connect them with the 

 cross-ribs in the finer ones, even with the widest-angled oil immer- 

 sion, but in the scales of the Amathusia they are plainly seen to 

 stand on them, and the structure is large enough to remove all 

 doubt. As nearly all scales present the same primary structure, is 

 it a very far-fetched conclusion to arrive at, that the fine beading 

 of the minute scales is fastened on in the same manner, even if 

 you cannot see the connection ? 



The scales of A mathusia are very interesting from their connec- 

 tion with historical microscopy. On the 20th of December, 1848, 

 Mr. \Varren De La Rue read a paper before the Microscopical 

 Society on the scales of this butterfly, in which he mentions and 

 draws the beading as seen by him on the cross-ribs. Illustrating 

 the paper is a fine plate showing the whole scale magnified 800 



Journ. Q. M. C, Series II, No. 20. 14 



