( xli ) 



the forest moths which I captured and compared with it. 

 If actually of butterfly origin it would suggest, once more, 

 that when butterflies are suflEiciently available birds may 

 even find it worth while to turn their special attention to 

 them — as Mr. H. C. Bryant has actually noted in California in 

 connection with the butterfly Engonia californica. 



I propose to deal with the whole question of birds and 

 butterflies far more fully in a future paper — after, I hope, 

 further stomach-examination work. 



The Bugalla Island case. — Col. Manders has objected to 

 Dr. Carpenter's suggestion as regards the greater frequency 

 in Bugalla of the transitional forms of a Pseudacraea which 

 there considerably outnumbers its Planema model, that 

 Bugalla Island is near enough to the mainland (where the 

 proportions are reversed) for birds to pass freely to and fro. 

 The solution to this question of bird-habits is, curiously, 

 provided by Bates himself in his very fascinating description 

 of the hunting-habits of the birds of Ega (" The Naturalist 

 on the Amazons," vol. ii, pp. 334-6 of the 1863 edition). I 

 have myself, year in and year out, noticed the same phenomenon 

 in our African birds. It is that the great mixed parties of 

 insectivorous birds that systematically and in combination 

 search the woodlands for their prey, each have a definite 

 limited area that they keep to and " drive " thus day after 

 day. There are two such main parties, each with its special 

 " beat," in that portion of the Chirinda Forest in which I 

 chiefly collect (I distinguish them from each other by the 

 presence of certain constant component members), and my 

 experience fully coincides with Bates' where he remarks : 

 " I became in course of time so accustomed to this habit of 

 birds in the woods near Ega, that I could generally find the 

 flock of associated marauders whenever I wanted it. There 

 appeared to be only one of these flocks in each small district." 



If birds by choice thus confine themselves to a given area 

 of forest — up to 200 acres to a flock is my estimate for 

 Chirinda, though a small isolated forest-patch of perhaps 

 forty acres separated from Chirinda by only a few hundred 

 yards of grassy hill-side boasts a flock of its own — will they 

 not, a fortiori, tend on the whole to keep within such islands 



