G86 Mr. C. F. M. Swynnerton on the 



butterflies piecemeal. The latter process is likely to be 

 particularly effective in quickly disguising the identity of an 

 insect with so weak a chitinous covering. In the case of the 

 only two Ploceids on which I have experimented, the 

 butterfly was commonly reduced by fine nibbling to a flat and 

 almost unrecognisable pulp even before it was swallowed. 



2, Some, probably most, insectivorous birds digest with 

 great rapidity, and they get rid of the chitin they have 

 swallowed in two ways : (1) crushed small, in the excreta; 

 and (2) in the form of pellets that are brought up at longer 

 intervals. It had been suggested to me by the examination 

 of the pellets and excreta respectively of several species, that 

 the wings of some of the insect-orders and the weaker chitin 

 generally are probably, as a rule, more rapidly and 

 thoroughly disintegrated than the harder portions, and that 

 much of the former may already be passing out through the 

 intestines and so lost to the stomach-examiner at a time 

 when the more obstinate fragments of the same meal are 

 still awaiting, in the stomach, their expulsion with the 

 next pellet ; and, so far as they w cut, a few special 

 experiments on specimens of L««?'m5, Laniarius, mid. Dicriirus 

 quite confirmed this view. 



3. In these experiments the wings of butterflies appeared 

 for tiie most part, both in the pellets and the excreta, as 

 narrow, oblong, transparent strips varying from roughly half 

 a millimetre to one and a half in length by, frequently, only 

 the distance between the rows of scale-bearing " collars."" 

 They were readily recognisable only under the microscope. 

 This thoroughness of disintegration, if it represents what 

 usually takes place, must be highly destructive to evidence, 

 and should be given full consideration. After large 

 butterfly-feeds of some of my captive birds I have often 

 (though not invariably) felt, in examining a pellet composed 

 almost solely of butterfly debris, that had I found that mass 

 in a bird's stomach and subjected it merely to the usual 

 rough examination, my verdict might well have been '^ Fine 

 insect-debris^ unrecognisable.'^ The special experiments that 

 I have referred to have aff"orded further excellent examples : 



