916 



Insects. 



seen with difficulty, and only upon a few scales. The regular undulations which are 

 often seen hetween the striae, and which are sometimes wanting in the part where the 

 striae have been rubbed off, have much assisted me in forming this conclusion. 

 If, as I have before said, the upper membrane carries the granulations forming the 

 colouring matter, and rendering the scales more or less opaque, and the lower mem- 

 brane is laden with striae, then the existence of a third membrane must be admitted, 

 otherwise the scales upon which are only seen stria? without granulations would have 

 but one membrane, which is contrary to observation. It might be argued, without 

 doubt, that it is possible that the same membrane might carry both striae and granu- 

 lations ; and this belief might be strengthened by the examination of opaque scales 

 partly stripped of their stria?, and where the spaces evidently show that both granula- 

 tions and striae have been removed. The discovery of certain scales showing similar 

 defects has proved to me that this is not the case. In truth, the portion of 

 the said scale upon which the granulations are found indicates clearly the existence 

 of the upper membrane, of which the tear seen is a complete proof, and the removal of 

 that portion which has been torn away lays open very regular series of striae before 

 concealed. It seems to me that this last portion presents the appearance of scales 

 with striae, and without granulations, and in which the existence of a double mem- 

 brane is proved. It is also shown in the same scale in the spots where the striae ap- 

 pear to have been removed. In fact, I am led to believe that three membranes exist 

 in all scales, and that where there are no granulations the upper membrane is so 

 transparent that it does not interfere with the appearance of the striae. It often hap- 

 pens that the lamellae of which the scales are composed, and which are united by a 

 border more solid than the other portions, are tinged with a reddish brown, which ap- 

 pears at first sight to penetrate the substance of the membrane. In examining these 

 membranes with a very high power, it appears that this tinge is due to a multitude of 

 irregular points touching on the transparent foundation. Slight striae, very difficult to 

 observe, can also be perceived. It is probable that these granulations aud striae, often 

 colourless, are always present, and according to the laws of the organisation of scales, 

 the first upon the upper, the latter upon the lower membrane. After having 

 described the use of the two upper membranes of the scales, I will now speak of the 

 third. The lower surface of this lamella, or of the second in the scales, where only two 

 are apparent, possesses, in all the diurnal and even in most of the nocturnal Lepi- 

 doptera, the power of reflecting rich and varied colours, always more beautiful than 

 those on the insect itself. The rich and brilliant scales found in abundance 

 in the various species of the genus Vanessa will alone show the most magnificent 

 colours. The most remarkable in this respect of the indigenous species are Vanessa 

 Antiopa, V. Atalanta, V. Polychlorus and V. Io. The scales of the exotic Lepidoptera, 

 composing the genus Vanessa, Nymphalis, and many others, reflect colours perhaps 

 even richer than those of the indigenous species. It must be remarked that it is 

 generally upon the dark parts of the wings that the most brilliant scales are to be 

 found. They are often opaque, and taken from any portion of the wing of the same 

 insect; they never vary in colour, though they sometimes do in brilliancy, in the same 

 species. The flutings of scales terminating in notches are often seen very distinctly 

 upon these coloured lamellae, but less so in the upper membranes. The same thing 

 occurs with the undulations seen in the lamellae, and which are often finely marked in 

 the scales covering the bodies of the diurnal Lepidoptera. The lower lamella? of a 

 number of the nocturnal Lepidoptera also reflect very beautiful colours, though not to 



