FEEDING-HABITS OF FISH AND BIRDS. 57 



The following are samples o£ the observations : — 



Obs. — " March 30. 1911, lake Okeraka, New Zealand, stomach contents of trout 

 were four grasshoppers, two cicadas, and three short pieces of stick of about the 

 same length and thickness as the grasshoppers. 



"■July 21, 1911, E. Kennet, Newbury, stomach contents were many ' Pale Watery 

 Duns ' (Ba'etis binoculatus) and three grass seeds similar in size to the bodies of the 

 insects. 



" July 5, 1909, R. Lambourne, Shefford, watched a fish for half an hour taking 

 ' blue-winged olives' (Ephemerella ignita, Poda) and ' Eeed Smuts ' (Simulium), fish 

 always examined any small floating object which at all resembled the insects ; 

 on more (ban a dozen occasions such things were mouthed, and twice, evidently 

 swallowed.'' 



More certain evidence that front are easily deluded is provided by the fact 

 that the dry-fly fisherman is able to kill fish with crude floating imitations 

 of, the natural insects made of fur and feather. Dry-fly fishing consists of 

 floating over the fish and making to rest on the surface of the water, a dry 

 artificial insect in imitation of the natural one on which the fish has been 

 observed to be feeding. In streams which are little fished the fish are 

 easily deluded ; but, in heavily fished waters, they become educated and are 

 able, on close inspection of the insect, to detect the counterfeit. This 

 education is the result of the fish having been either caught and returned, 

 or hooked and lost on many occasions. The Plate (PI. 5) shows a series of 

 artificial insects photographed against a high light, as the fish see them. 

 It illustrates the roughness of their resemblance to the natural insects. 

 The artificial insect may be looked upon as an unpalatable insect mimicking 

 a palatable one, and the facts show that a crude mimicry is of considerable 

 power for delusion. 



Observations which indicate that Birds mistake inanimate things for Flyinq 

 Insects, and the Angler's Fly floating on the water for Insects similarly 

 situated. 



If Muscicapa grisola (spotted flycatcher) or any of the species of swallows 

 or martins be watched, over a long period of time, whilst the)' are feeding on 

 flying insects, it will be noticed that not infrequently the birds start out from 

 where they are resting, or alter their line of flight, in order to capture small 

 pieces of feather, seed-plumes, leaf- scales, chaff, or other light bodies floating 

 in the air, which they obviously mistake for flying insects j as a rule, closer 

 inspection shows them their mistake. Sometimes the object is taken in the 

 bill and subsequently dropped ; or very occasionally it appears to be 



LINN. JQURN, ZOOLOGY, VOL. XXXIV. 5 



