﻿CHEMISTRY OF INSECT COLOURS. 309 



Although I have reason to believe I have been exceptionally for- 

 tunate, I never reared more than half-a-dozen at a time. 



Turning over my notes, I find the emergence of the bred 

 insect to occur between the 5th and 21st of April. There is, I 

 think, little fear of confounding this species with T. instabilis. 

 In the type insect all the wings, but especially the fore wings, are 

 a beautiful silvery grey, with a broad, transverse, median brown 

 bar, which is widest at the costal margin. On the widest half of 

 this bar the discoidal spots are clearly marked out in the same 

 silver-grey. Parallel with, and at a short distance from, the hind 

 margin, the wing is again crossed by a rich, direct, brown line, 

 which is exteriorly bounded by another line almost white. The 

 fringes, especially those of the hind wings, are almost white. 

 The antennae of the males show a slight pectination ; tbe thorax 

 is a little darker in shade than the ground colour of the win^s, 

 while the body is a shade darker than the thorax. In the second 

 form of the moth the fore wings are a rich dark brown, the hind 

 ones being slightly paler in tint. All the markings of the fore 

 wings, however, are clearly visible, being intensified in colour. 

 The body and thorax are also proportionately darkened. The 

 coloration in both forms of T. opima is clear, distinct, and con- 

 stant, in all the specimens I have seen, whilst T. instabilis can 

 lay no claim to these characteristics. 



I have never captured the perfect insect. Mr. Grearley, of 

 Wallasey, tells me he has taken both forms — freely in exceptional 

 years — at the sallow blossom. 



CONTRIBUTIONS to the CHEMISTRY of INSECT COLOURS. 



By F. H. Perry Coste, F.C.S. 



(Continued from p. 287). 



V. — The Chemical Aspect. 



B. 



After the explanatory digression of last month we are now 

 free to consider the experiments on each colour individnally : 

 and first, then, as to Black, that prince of absorption colours. 

 It is very commonly told us, on excellent authority, that we 

 learn more from our failures than from our successes : possibly 

 — but I have some doubts thereupon ; and if the sentiment be 

 expressed by way of consolation, it is surely the consolation of a 

 Job's comforter. Anyhow, be that as it may, I am very certain 

 that our failures do not teach us nearly so much as the successes 

 that we desired would have done. To particularise, for my own 

 case, it must be admitted that all my endeavours to learn some- 

 thing of the relationship between black colour in Lepidoptera 



