Wing, wing-sciales, and their pigments IN butterflies and moths. 161 



latter contains the materials necessary for going through the chemical 

 change resulting in pigmentation, 



Mayer has made a chemical analysis of the pupal blood, which agrees 

 with that made by Landois. When the hremolymph is agitated with 

 ether, the proteid substances are coagulated, and a clear amber-yellow 

 solution is left. When thus isolated the proteids are shghtly yellowish, 

 but they soon dry into a drab-coloured mass, very much as the ha^mo- 

 lymph does upon exposure to the air. Spectrum analysis shows that 

 the colour of the amber-yellow solution is due to xanthophyll, and 

 Poulton found that the colours of many lepidopterous larvte and 

 pupfc were due to chlorophyll and xanthophyll, derived from their 

 food. The hnsmolymph is acid to litmus, and contains a large 

 amount of orthophosphoric acid. The mineral bases of the htemo- 

 lymph are iron, potassium and sodium — -the iron in considerable 

 quantity. " The freshly-obtained hiBmolymph is a clear opalescent 

 amber-yellow fluid ; it soon becomes turbid upon exposure to the air, 

 and in less than half-an-hour after removal from the chrysalis be- 

 comes opaque, and drab or greenish-drab in colour." Mayer further 

 notes that the drab colour, assumed by the dried hfemolymph from 

 the pupa of CalloKaniia pwiiicthea, and the greenish-drab assumed by 

 the dried hsemolymph of Philosamia ci/nthia, are very similar to the 

 principal colour of the moths' wings. The change in colour exhibited by 

 the hsemolymph upon exposure to the air is probably not due to a 

 simple process of oxidation. It takes place slowly in an atmosphere of 

 hydrogen ; an atmosphere of CO.^ prevents it ; whilst, if the ha^mo- 

 lymph be sealed up in air-tight glass tubes, it retains its amber colour 

 indefinitely. Heated to 54^0, it begins to congeal, and above 63*^C 

 solidifies into a chrome-yellow mass, and in this condition it will keep 

 indefinitely, and retain its original chrome-yellow colour ; but when 

 congelation is produced in htemolymph that has become drab by 

 exposure to air, the congealed mass is also drab in colour. 



To test whether the colours of the mature wing are derived by 

 various chemical processes from the hsemolymph of the pupa, 

 Mayer performed the following experiments : (1) He treated the 

 haemolymph of Samia ccr^vyx'rt with warm concentrated HNO 3, when 

 it congealed into a deep chrome-yellow mass. Ammonia (in excess), 

 added to this, changed it to reddish-orange, very similar in colour to 

 the reddish-orange band that crosses the upper surface of the hind- 

 wings of the moth. The reddish -orange band of the moth is changed 

 to chrome-yellow by HCl or HNO3, and, on ammonia being added, 

 the original red colour returns. Exactly the same sequence of 

 reactions is produced with the pigment derived from the htemolymph. 

 (2) Treating the drab-coloured outer edge of the wing of S. cecrupia 

 with warm HNO3, and evaporating the acid off at a gentle heat, the 

 drab pigment of the scales was found to be changed to a deep chrome- 

 yellow. The addition of ammonia makes it reddish. Similar reactions 

 are obtained from the hfemolymph, after it has congealed in the air, 

 into a greenish-drab mass. (3) The drab hsemolymph of C'allo><amia 

 prnmethea is dissolved and changed to a sepia-brown colour by warm 

 HCl, to which a crystal of KCIO3 is added. An exactly similar 

 change occurs when the drab-coloured edges of the moths' wings are 

 treated in a similar manner. 



These experiments, like those of Coste {Entomulutjiat, 1891, ct seq.) 



