21 
however, remarkable that the larve of so fat and greasy a moth should be nourished 
on so dry a substance as bran. Mr. Dunning thought the larve were more probably 
those of Pyralis farinalis; and Mr. Newman suggested Ilithyia sociella. 
Prof. Westwood exhibited nine species of Charaxes (three of which*were unique 
specimens) from the Zambesi, whence they had been sent by the Rev. H. Rowley; 
each specimen was placed in a separate envelope, a considerable number might thus 
be placed in a box, and the whole had travelled in this manner without sustaining 
material injury. 
Mr. A. R. Wallace exhibited various“species of Papilio, Eronia and Pieris, with 
the intention of showing the effect of locality in producing change of form in insects. 
Numerous species inhabiting the island of Celebes were produced, and in each case in 
juxta-position therewith was its nearest ally from the adjoining islands. The Celebes 
insects, in every instance exhibited, had the costa of the anterior wings much more 
strongly arched than was the case with their congeners with which they were 
compared. Mr. Wallace remarked that changes in colour which were due to locality 
had been frequently noticed, but of instances of a change of form only few had been 
recorded; Mr. Bates, however, had mentioned some as having come under his obser- 
vation in South America. In the Eastern Archipelago, he (Mr. W.) had found that 
the butterflies inhabiting the islands which formed the eastern half were generally 
larger than those in the western half; and, especially in the Papilionide, that Celebes 
and Amboyna produced the largest specimens. Some species which in India were 
found with a large tail appended to their hind wings, possessed only a small tail in the 
Indian Islands, which ceased altogether or was reduced to a mere tooth in the islands 
of the Pacific; of this Papilio Agamemnon was an example. The island of Celebes 
was as nearly as might be the centre of the Eastern Archipelago, and the butterflies of 
that island, especially the Papiliones, possessed the peculiarity in the form of their wings 
to which he had invited attention; sixteen or seventeen species of Papilio were found 
in Celebes, and, with a single exception to be afterwards noticed, all were distinguished 
from their allies in the other islands by having the upper wings strongly arched, in 
lieu of a gentle and gradual curve, or, if he might so term it, a flat bend. The same 
distinction existed also in many Pieride and in a few Nymphalide, but he had not 
observed it in other groups of butterflies. Mr, Wallace bad a theoretical explanation 
to offer of this phenomenon; he conceived that the insects had become modified in 
form by the external circumstances to which they had been subjected, and that this 
modification was to be accounted for by some physical or organic change which had 
occurred in Celebes, but not in the now adjacent isles. Rapidity of flight was gene- 
rally supposed to be the consequence or a property of the falcate form of wing; he 
(Mr. W.) was inclined to think that the falcate form gave greater facility in twisting 
or turning about; if that were so, the Celebes form of butterfly-wing would give the 
insect this additional facility, and thus enable it more easily to escape from its enemies. 
If, then, the Celebes insects were supposed to have been formerly subject to great per- 
secution, those with the arched form of wing would have the best chance of escaping, 
the less favoured forms would be gradually killed off, those that survived would owe 
their existence to the form of their wings, their offspring would resemble and some few 
would exceed them in the possession of the advantageous shape, and the specimens 
with the best developed wings being naturally selected in each succeeding generation 
would lead to the gradual and regular increase of the peculiarity. But then it might 
be asked, How is it that only a few of the butterflies have the peculiarity in question ? 
