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I July— Aus"^<l iSS.V 



most often imbricated and usually cause 

 more lustre than hairs. Hairs or scales 

 nia\ he of a ditierenl color from the 

 surface on wiiich they are placed. If 

 thev are numerous and opake thev max 

 entirely conceal the sm'face on which 

 they are inserted, as the white hairs 

 hide the bronze surface of the sides of 

 the thorax in Cicindela dorsalis. and 

 as the white scales of Alans oculatiis 

 hide the black surface beneath the rings 

 on the thorax ; or they may only partly 

 conceal the surface of the insect, giving 

 rise to coarser and finer mixtures and 

 shades of color. Opake scales, or 

 hairs, of more than one color, may cause 

 figuration, whether the\ imbricate as on 

 the \\ ings of lepidoj)tera, or are separ- 

 ated as on Autlirciiiis scrophulariae. 



The possibilities of varying effects 

 of color are many with opake scales 

 and hairs, but \yith transparent ones. 

 especialh if the\' are colored, the effects 

 of color can be multiplied still further. 

 With hairs the effects are not so re- 

 markalde as with scales. The scale, by 

 its form, increases the number of la\ers 

 of the surface of an insect which are 

 available for colorational purpo.ses. 

 Where the surface of an elytron had 

 previously a cuticular and hj'podermal 

 la\er. 1)\' the addition of a scale of tlie 

 simjilest type there is an addition ot 

 two cuticular and, theoretically at least, 

 two hvpodermal or sub-cnticular layers ; 

 in all six layers, without counting over- 

 lappings of imbricated scales. Some 

 of these surfaces may have pigments, 

 striae, hairs and other appliances to 

 produce colors, and other surfaces may 



ha\e other striae and contrivances to 

 act on the colors produced. The nu- 

 merous niodilications need not be enu- 

 merated here. I have alluded to sjjecial 

 effects of coloration in describing the 

 scales of different insects and shall 

 again refer to some of them when dis- 

 cussing the modes by which the scales 

 themselves are colored. I max add here 

 that the general effect of transparent 

 scales is to produce metallic coloration. 



The kinds of coloration in coleoptera 

 have been neatly tabulated by Fischer, 

 according to the families of these in.sects. 

 I translate his table, making in it. a few 

 alterations based upon my own obser- 

 vations and indicated by italics. i^See 

 itext page. ) 



Next to tiie consideration of how the 

 color and presence of scales and hairs 

 affect the appearance of surfaces to 

 which they are attached is the not less 

 interesting question of the causes of 

 coloration in scales themselves. Rut 

 l>efore considering the causes of color. 

 propel Iv speaking, a few words are 

 appropriate on the causes which pro- 

 duce silverx and milk-w hite appearan- 

 ces in scales and on insects. Levdig 

 was the first, in 1855, to call attention 

 to the presence of air between or be- 

 neath their chitin laxers as a cause for 

 certain silverx' spots an<l scales on in- 

 sects. He speaks of air in the fine!' 

 pore-canals of Ixodes testudii/i's. gi\ - 

 ing these canals a black appearance. 

 but causing the whitish grey color of 

 the skin. So too he mentions sil\ er\ 

 scales on a spider. Sa/ticits. ancl glis- 

 tening hairs on another spider. Chibioiie 



