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SUMMARY OF CURRENT RESEARCHES RELATING TO 
only so long as the wing remains acid ; as soon as the acid is entirely 
removed, either by copious washing with water, or neutralization with 
ammonia, or by prolonged drying (exposure to the air for some weeks) 
the original red returns. 
These phenomena are explained by assuming that the acids form 
probably molecular compounds with the red pigment molecule, thus 
producing yellow pigments ; these molecular compounds being unstable 
are readily decomposed by excess of water, or by gradual oxidation (?) as 
in the air-drying experiments, leading to the restoration of the original 
red. In the case of nitric acid, it is clear that instead of the formation 
of such molecular compounds, a destructive action on the pigment 
molecule has taken place. 
Chestnut or brown is very closely similar in character and be- 
haviour to yellow ; here too he distinguishes three stages of solubility, 
corresponding with those in yellow, and he also thinks it possible that 
some of the insoluble chestnuts also maybe “ physical ” colours, and not 
pigmental at all. He finds further that a few reds (e. g. in V. Atalanta) 
have been evolved not from yellow, but from chestnut : these reds do 
not show the “ reversion ” effect. 
Among the greens some are certainly physical ; some are probably 
physical ; and some are pigmental. The first class includes all the 
metallic greens ; these may be either unaffected, or temporarily or 
permanently dulled or browned by the reagents ; the alteration in such 
cases is to be attributed to injury of the molecular structure of the wing. 
The second class of greens are instantly changed to brown, or bronze- 
brown : these, too, are probably physical. The third class are dissolved, 
leaving a white wing : in some cases, however, a more or less yellowish 
white, and occasionally a deep yellow, are produced; it is therefore very 
probable that green also has been evolved from yellow. 
Blue is an unsatisfactory colour from the author’s point of view. In 
nearly every instance he finds it to be physical in nature ; and the same 
general account may be given of these physical blues as of the physical 
greens. As to the blue of the Lycsenid£e, however, the author reserves 
his opinion for the present, although strongly inclined to consider this 
also a “ physical ” blue. 
An account of the reaction of very damp potassic cyanide on certain 
yellow species is also given. The author’s attention was called to this 
matter by a reported experiment of Edwards concerning which he 
was formerly very sceptical. He now finds, however, that in many 
species of Rhopalocera (no such results have yet been obtained from 
yellow Heterocera) the yellow, under these conditions, is changed to a 
more or less brilliant red ; this is extremely interesting as being an 
instance of progressive modification. The author thinks it probable 
that in such cases, combination takes place between the pigment mole- 
cule and the cyanide radicle : but he is still employed in investigating 
the subject. 
In the last section of his paper, the author remarks on the general 
chemical effect of soil, food, and the like, on the colours of insects, and 
suggests an explanation of several varieties such as white specimens of 
E. Janira , Lycsena phloeas, Colzas helice , &c., and finally points out, by 
quoting details, the interesting fact that in the course of his experiments 
