28 



THE. YOUNG NATURALIST. 



infinitely more minute than) the feathers of birds. 

 This is what De Geer thought, nor was he after 

 all far from the truth, as we shall presently see 

 from the studies of subsequent observers. Reaumer 

 gave them the name which they now bear, namely, 

 that of " scales," from their being composed 

 of small membranous plates, or layers of delicate 

 tissue. Scales vary greatly in size, and it would 

 be a mistake to suppose that the largest insects are 

 those thaf have largest scales, as the reverse is fre- 

 quently the case, those from the wings of the Micro- 

 Lepidoptera often exceeding considerably in size 

 those of the Macros. The surface of the scales is 

 covered with longitudinal lines, or striae, crossed 

 again with others transversely. These are in 

 reality wrinklings in the delicate tissue . Besides 

 the striae there are also, says Dr. Pigott, small dots 

 or beads which he states are dried drops of some 

 secretion which is upon the scale when the whole 

 wing is moist immediately after metamorphosis. 

 Mr. Jabez Hogg dissents from this generally 

 received opinion and remarks that "these qnasi- 

 beads are solely due to diffraction phenomena, and 

 increase of chromatic aberration, the bead -like 

 swellings or dots are simply aggregations of minute 

 particles, retained between layers of membrane, 

 thrown into wavy longitudinal folds, again crossed 

 by ribs of striae. These, when slightly out of 

 focus, appear as varicose dots or beads. This is j 

 fully confirmed by careful focussing when first the j 

 upper series of varicose ribs come into view, then j 

 by slightly depressing the objective a lower set is 

 seen, the upper set almost disappearing. By 

 another slight movement of the fine adjustment 

 the true ribs are lost sight of, and the "exclamation 

 dots come into view." 



Dr. Duncan makes this assertion, "The micros, 

 cope has proved that no inherent and tangible 

 colouring matters exist in these tiny dust-like 

 particles. The delicate ridges and network of the 

 scales act upon the colourless rays of light that fall 

 upon them and decompose them into a variety of 

 tints that emulate the rainbow." Is it so, or are 

 we to believe with others who as emphatically 

 affirm the existence of pigment granules ? In my 

 humble opinion both theories have truth in them, 

 for doubtless that beautiful exhibition of varying 

 colours to be seen in some species, more especially 

 amongst exotic lepidoptera, when the wings are 

 in different positions, is produced by interference 

 and the decomposition of the rays of light ; on 



■ 



the other hand, it seems to me that there must be 

 some colouring matter in the scales, and my 

 reason is this. On many insects, acids have a 

 remarkable effect in changing the colours, partic- 

 ularly green tints, altering them to a bright orange 

 or coppery red : must we not suppose that this is 

 due to some chemical change ? I am at a loss to 

 understand how a change could be brought about 

 if there be nothing in the scales upon which to 

 work. And again, if it. be true that the colours 

 of lepidoptera are much modified by the food on f 

 which the larvae fed, it is not likely that any! 

 alteration is caused in the structure of the scales ;| 

 but rather that a change is effected in the pigment 

 granules. 



The arrangement of scales upon the wings is very'' 

 regular, resembling that of the slates in a roof 

 The hairs and down with which the bodies of 

 moths and butterflies are covered, are of the samei 

 character as the scales which clothe the wings,: 

 being simply modified scales. 



Somewhat analagous to those of lepidoptera 

 but far surpassing them in brilliancy, are the scale*'! 

 of certain species of beetles. In this country the)!) 

 are confined to the vast group of Rhyncophora oijp 

 weevils. To see them however in their full splenW 

 dour we must seek for them amongst the tropical* 

 Buprestidce and Cetoniadce, some examples t< f 

 which fully warrants the language of that accomi f- 

 plished microscopist Mr. GossEwhenhe says "W i; 

 see a black ground on which are strewn a profusio; 

 of what looks like precious stones, blazing in th 

 most gorgeous lustre — topazes, sapphires, ame 

 thysts, rubies, emeralds, seem here sown broadcast 

 Although there is a resemblance to the scales 

 butterflies and moths they differ in many impoi 

 tant particulars. They are not as a rule cross 

 with striae, or indeed have any marks at all, tr 

 surface being smooth and polished, though in som 

 of the exotic species I have discovered striae em 

 with a one inch objective. They appear to I 

 perfectly fiat and in shape generally that of an egj 

 Then there is this notable distinction, they a! 

 without any footstalk, and the way in which t 

 are attached seems not to be known. It is wi 

 these magnificent scales are prepared those mi 

 vellous triumphs of ingenuity and skill inmounti 

 the costly "bouquet" slides, representing flowed 

 birds and insects. 



The beautiful velvet coat of the Humble B 

 the feathers of Birds, the scales of Butterfli 



,e 



