Boyal Microscopical Society. 253 



in the " finest and most transparent scales of ' azure blue,' " hence 

 we must consider, whatever be the true structure of the " Test 

 scale," the Lepidoptera scale is of the same nature. This admitted, 

 it becomes easy to show that the Lepidoptera scale, though furnish- 

 ing more or less all the optical appearances of the " Test scale," is 

 in reality not constructed after this method. Thus a doubt is at 

 once raised as to the correctness of the view entertained of the 

 structure of the scale of Lepiclocyrtus curvicoUis, and its congeners. 



Before touching the microscopical investigation of the Lepidop- 

 tera scale, it may be as well to ask if we have in any dermic struc- 

 ture of the animal series one composed of beads lying either side of 

 a basic membrane ? I know of none, though of course it does not 

 follow such may not exist ; therefore these remarks are open to cor- 

 rection. But what possibly is the function of so elaborate a struc- 

 ture as found in the scales of the Lepidoptera and Thysanuradeas 

 generally ? 



Sm^ely little can be founded on such a beaded structure, whether 

 for strength in the arrangements, or function, beyond a covering 

 and the power to intensify their iris hues ; though if we admit that 

 the generally-received opmion respecting the scale of the Lepi- 

 doptera is more correct, as I shall show farther on, then by the 

 substitution of a true framework for beads, we obtain strength, and 

 from its position may eventually find some greater purpose to be 

 effected in the economy, beyond contributing to those wonderful 

 iridescent qualities and common tegumentary relations ; and which, 

 possibly, is one efi'ecting a change in their semi-fluids by the action 

 of the external air through deUcate investing membranes. 



All recent scales that have been examined gave more or less 

 evidence of containing some greasy semi-solid material within the 

 membranes ; and possibly it will be found the more the body of the 

 bearer partakes of this fatty nature, the more also the scales partici- 

 pate. Such seems to be the case in the large fatty-bodied moths. 

 This, doubtless, largely facilitates the resistance to wet, which in 

 the case of the Lepidoptera would otherwise be almost fatal to their 

 flight. 



In my micro-chemical investigations of some of the common 

 butterfly scales, and which Mr. Mclntire did me the honour to 

 insert as a note to his paper " On the Minute Structure of the 

 Scales of certain Insects," * it was found the contents of the scale 

 could be in part removed by various solvents. In addition to 

 those experiments, to which reference is made, strong sulphuric 

 and nitric acids, &c., have been tried, with the hope of obtaining 

 better characteristics of the internal structure; but perhaps the 

 most satisfactory plan has been to char the scales, — a suggestion 

 taken from one of my friend Mr. Wenham's letters, to hand some 

 * ' M. M, Journal,' No. XXV., p. 3. 



