We have no positive evidence that these birds pursue butterflies on the wing, but it is highly probable that they do so when other food is scarce.

Mr.Bates suggested to me that the larger dragon-flies prey upon butterflies, but I did not notice that they were more abundant in Celebes than elsewhere."[66] Now, every opinion or conjecture of Mr.Wallace is worthy of respectful and attentive consideration, but the explanation suggested and before referred to hardly seems a satisfactory one.

What the past fauna of Celebes may have been is as yet conjectural.

Mr.Wallace tells us that now there is a remarkable _scarcity_ of fly-catchers, and that their place is supplied by birds of which it can only be said that it is "highly probable" that they chase butterflies "when other food is scarce." The quick eye of Mr.Wallace failed to detect them in the act, as also to note any unusual abundance of other insectivorous forms, which therefore, considering Mr.Wallace's zeal and powers of observation, we may conclude do not exist.

Moreover, even if there ever has been an abundance of such, it is by no means certain that they would have succeeded in producing the conformation in question, for the effect of this peculiar curvature on flight is by no means clear.