9086 Entomological Society. 
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 eentre 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 afierwards noticed, all were distinguished 
from their allies in the other islands by haviug 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 faleate 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 ? 
The answer was, that different insects preserve their existence by different means; one 
may escape by means of its power of flight, the habits of a second may enable it to 
avoid its foe, a third may owe safety to its colour, whilst a fourth may be positively 
distasteful to animals which prey upon insects. Thus the Danaidz, though slow of 
flight, were very abundant and were the subjects of mimicry or imitation by other 
species; in all probability they owed their immunity from destruction to the strong 
and unpleasant odour which they indubitably possessed. It was manifest that where 
another means of escape already existed, the principle of selection would not be 
brought into play; the peculiar form of wing would not be wanted, and therefore 
would not be acquired. The obscure Satyride were doubtless protected by their 
colour; the majority of the Nymphalidw had already sufficient power of flight, and 
those of that group which had acquired the arched form of wing were precisely the 
species which possessed only about the same power of flight as a Papilio, The single 
Celebesean Papilio which had not assumed the arcuate form of wing was one belonging 
to the Polydorus group, a group which was itself imitated by other Papiliones, and 
which therefore was doubtless provided with some special defence, though the nature 
of it was unknown to us. 
Prof, Westwood, after remarking upon the pleasure he always derived from 
Mr. Wallace’s speculations, whether he agreed with them or not, said that he was 
unable to follow Mr. Wallace in tracing the phenomenon to the causes assigned by 
him; arched wings were not necessarily, or even generally, accompanied by the 
greatest rapidity of flight; and if the original form of the butterfly must be varied, if 
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