202 TEXT-BOOK OF ENTOMOLOGY 



"The scales of Entimus and other Curculionidae are well known for their 

 brilliancy, and it is interesting to remark that when dry scales are examined with 

 the microscope, many are found partly injured, which give in different places 

 different colors, according to the number of layers which remain. The elytra 

 of some Chrysomelina and other beetles with iridescent colors probably belong 

 to the same category. 



"2. When there are scales with many fine lines or small impres- 

 sions close to each other, we have the second mode of producing 

 colors. 



"The fine longitudinal and transversal lines of lepidopterous 

 scales seem to serve admirably well to produce the brilliant effect 

 of color-changing butterflies. But there must be something more 

 present, as most of the scales of Lepidoptera are provided with 

 similarly fine lines, and only comparatively few species change 

 colors. I remark purposely that the lines in the color-changing 

 scales are not in nearer juxtaposition." (Hageu.) 



"The colors of butterflies change mostly from purple to blue, sometimes to 

 yellow. The splendid violet color at the end of the wings of Callusune ione is 

 brought out by a combination of the natural with interference colors. Origi- 

 nally the scales are colored lake-red ; but a blue interference color is mixed with 

 it ; hence the violet hue results. The blue tones, i.e. the splendid varying blue 

 of the Morpho butterflies, Schatz claims, owe their hue less to the interference 

 of light than to a clouded layer of scales situated over the dark ground, through 

 which the light becomes reflected on the same. The scales of the Morphids are 

 in reality brown, as we see by transmitted light ; moreover, only the upper side 

 of the scales sends off blue reflections the under side is simply brown. But 

 the blue scales of Urvilliana are also shining blue beneath ; by transmitted 

 light they appear as if clear yellow. The smaragd-green scales of Priamus 

 show by transmitted light a bright red-orange, and the orange-yellow of Croasus 

 a deep grass-green." (Schatz in Kolbe.) 



" Krukenberg presumes the golden-green color of Carabits auratus to be an 

 interference color. It is not changed by the interference of light, nor was he 

 able to extract from the elytra any green pigment with ether, benzol, carbon 

 of sulphur, chloroform, or alcohol, even after having previously submitted the 

 elytra to the influence of muriatic acid or ammonia. Chlorophyll is not present, 

 whether free or combined with an acid." (Hageu.) 



Leydig has shown that the interference colors of the hairs of certain worms 

 (Aphrodite and Eunice) may be produced by very small impressions in juxta- 

 position, which bring about the same effect as stride. Such an arrangement 

 occurs on the feathers of birds, i.e. on the necks of pigeons and elsewhere, and 

 Hagen suggests that this kind of interference colors occurs more frequently 

 among insects than is commonly known. At least the limbs of certain forms 

 appear yellow, but when held in a certain position change to brown or blackish. 

 "I know of no other explanation of this not uncommon fact on the legs of 

 Diptera, of Ilymenoptcra, and of Phryganida;." Interference colors, he adds, 

 may occur in the same place together with natural colors. "The mirror spots 

 of Saturnia pernyi show besides the interference colors a white substance in the 

 cells of the matrix, which Leydig believes to be guanin. But this fact is denied 

 by Krukenberg for the same species and also for Attacus mylitta and Plusia 

 chrysitis." 



