54 THE ENTOMOLOGIST. 



keep indefinitely, always retaining its original chrome-yellow 

 colour. In like manner congelation can be produced in haemo- 

 lymph that has become drab by exposure to the air, only in this 

 case the congealed mass is dral3, not chrome-yellow in colour. 



If, in accordance with my hypothesis, it be true that the 

 colours of the mature wing are derived, by various chemical 

 processes, from the hfemolymph of the pupa, then one ought to 

 be able to manufacture various colours from the hfemolymph by 

 means of chemical reagents. Also, if the colour so manu- 

 factured be similar to some colour upon the mature wing, it may 

 be expected to present reactions to chemical reagents similar to 

 those of the colour on the wing. As far as my rather limited 

 experiments go, I find this to be the case. For example, if one 

 treat the hfemolymph of S. cecropia with warm concentrated 

 HNO3, it congeals into a deep chrome-yellow mass. If now 

 ammonia be added in excess, it changes to a reddish orange, 

 which is very similar in colour to the reddish orange band that 

 crosses the upper surface of the hind wings of the moth. Now 

 this reddish orange band of the moth is changed to chrome- 

 yellow by HCl or HNO3, and then, if ammonia be added, the 

 original red colour reappears ; this alternation of red and yellow 

 may be produced indefinitely by the successive additions of am- 

 monia and acid. Exactly the same sequence of reactions is pro- 

 duced with the red pigment derived from the htemolymph ; HCl 

 or HNO3, causes it to become chrome-yellow, and then ammonia 

 restores the original red colour. 



Another confirmatory test of a similar nature may be per- 

 formed as follows : A portion of the drab-coloured outer edge of 

 the wing of S. cecropia is treated with warm HNO3 and the acid 

 evaporated ofl; at a gentle heat. By this means the pigment of 

 the scales is changed to a deep chrome-yellow ; if ammonia be 

 then added, it becomes reddish. Very similar reactions are 

 obtained from the haemolymph after it has congealed, in the air, 

 into a greenish drab mass. 



Another experiment which I have tried is the following : — 

 The freshly drawn hsmolymph from a pupa of C. promethea is 

 congealed by heat into a chrome-yellow-coloured mass, then 

 HCI3 and a small crystal of KCiOa are added, and the acid is 

 evaporated ofi' at a gentle heat, By tbis means a purple mass 

 is produced, which is changed to drab by HNO3. The purple 

 spots near the outer edges of the hind wing of the female moth 

 are also changed to drab by HNO-j. 



Still another confirmatory experiment may be given. The 

 drab h^molpymh of C. pyoinctlwd 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 outer edges of the moth's wings are treated in a 

 similar manner. 



