562 
BIONOMIC NOTES 
sun becomes overclouded, it will sometimes close its wings 
and almost lie down, in such a manner that, to distinguish 
its brown and green marbled underside from the dead leaves is 
almost impossible/’ 1 
Here Barrett says if the sun becomes overclouded, but I have 
observed the list (in other butterflies) during bright sunshine only. 
It will be remembered that Prof. Parker (p. 539, supra) states that 
some American species of the genus Grapta orient themselves, so 
that it would appear that both heliotropism and list occur in the 
same genus. 
When my attention was first drawn to the subject of heliotropism 
by observing the habits of Pararge schahra, Koll., in the Simla district 
in October, 1903, I was disposed to associate that habit with list, 
and suggested that both had probably been selected, since they 
appeared to assist to a notable degree in the concealment of the 
insect from its foes. The evidence now available is more ample, 
though still far short of what would be requisite to establish definitely 
any explanation. 
Prof. Parker’s explanation that by negative heliotropism the 
insect displays its colouring to the best advantage, can scarcely be 
applied to list, for while it may be true that by listing a butterfly dis¬ 
plays its underside, that underside is in listing butterflies usually 
cryptic, even when in our cabinet it appears the more brilliant of 
the two. Moreover, in the listing position the most conspicuous 
feature of the pattern is often concealed by the hind-wing, so that 
the listing butterfly exposes to the sun one hind-wing only, and a 
small portion of the corresponding fore-wing. 
That under special circumstances there is an economy of shadow 
in both heliotropic and listing butterflies is unquestionable. On the 
other hand, the negatively heliotropic butterfly with wings expanded, 
and the listing butterfly with wings closed, both place their wings as 
nearly as may be normal to the sun’s rays, exposing in the one posi¬ 
tion their upper, in the other their under, surface. Is it possible 
that the direct rays of the sun, falling normally on either surface of 
the wings, afford a pleasurable sensation to the insect ? Or is the 
exposure of the insect’s body to the sun, common to some extent to 
both these attitudes, the end obtained ? The obvious love of most 
butterflies for hot and sunny corners unquestionably suggests some 
such explanation. Perhaps the two explanations may both be true, 
-—that heliotropism and list combine the pleasures of isolation with 
1 Op. cit., p. 125. 
