GEXEEAL ADAriATlOXS 347 



(the Bismarck Archipelago) there is a day-flyinn; i,„,th 

 (Burgena chalyhcata), one of the A<:aristifhi', wIkjso wings 

 change from Mack to blue and a fiery opalcsci-nt red. In 

 tropical America there is a group (»f hutterilies of tlic g«-nii8 

 Papilio, which are very abuii(hiiit botli in species and in«livid- 

 uals, whose velvet-black wings liav(^ a few bands or -jiois uf 

 blue or green on the upper pair, while the lower have a ban<l 

 of spots near the posterior margin of a brilliant cTimsnn. 

 Among perhaps a hundred species with this general style oi 

 coloration, there are a few (perhaps a dozen) in which ihe 

 red of the hind wings, when viewed very obli(iu('ly fn^ni be- 

 hind, changes into opalescent and then into a curious bluish 

 phosphorescence of intense brilliancy. 



I am informed by Dr. K. Jordan (of the Tring Zoohtgical 

 Museum) that in these insects the black ground of the wing 

 changes also into metallic blue, which seems to spread over 

 the red and to aid in the production of the phosphorescent 

 effect. This is so marked that ^Ir. Bates gave to one of the 

 new species he described, the name of Papilu) phosplionis. 

 One of the small Er^'cinidae (Euseldsia prcvclara) found in 

 the Upper Amazon valley, is of a yellow butf colour, with a 

 wonderful opalescent reflection which is said to be tlic most 

 intense and brilliant in the whole order of Lepidoptera iuid 

 probably the most brilliant colour known. 



All metallic reflections in the animal world are what aro 

 called interference-colours, and are prttduced by excessively 

 fine lines or rugosities on polishe<l surfaces, or by ('<iually 

 thin transparent lamina^. It is probable that in the remark- 

 able changing glows now described, l)olh these eauses may 

 come into play, producing, wlion viewed at eertain auirles, 

 an intensity of hue resembling those of the linest opals, or 

 sometimes imitating the most brilliant glow-worms or fire- 

 flies bv means of reflecteil light. It se(Mn< |»rol)able that tliCi^e 

 rare hues mav be nt' a pi-oleetivc nature, siui-e a pur-ning bird 

 miiilit be start le(l hv tli*' sudden fla-hinrr out of -n l)rilliant a 

 light and thus allow the inject to escape: lnu that dor'< not 



