310 



SCIENCE. 



[N. S. Vol. XXIV. No. 610. 



Here I was gratified in being able to ascertain 

 how he finds where to peck through the scales of 

 bark, so as to be sure to hit the apple worm that 

 is so snugly concealed beneath. The sense of 

 smell will not account for it. Such an acutenesg 

 of one of the senses would be beyond the imagina- 

 tion. Instinct, that incomprehensible something, 

 might be called in to explain to those who are 

 satisfied to have wonders accounted for by means 

 that are in fact only confessions of ignorance. 

 Birds have instincts undoubtedly — so have we; but 

 they are mixed up confusedly with other faculties. 

 Most of the actions of insects are purely instinct- 

 ive and utterly unaccountable. But the apple 

 moth is not a native of this country — the downy 

 woodpecker is. The bird would not have been 

 created with a special instinct to find the larva 

 of a moth that did not exist in the same country. 

 Other insects live under these scales of rough bark; 

 but in very numerous examinations, I have not 

 seen such a hole made except when leading directly 

 into the cocoon of this particular caterpillar. 

 This little bird finds the concealed larvae under 

 the bark, not from any noise the insect makes; 

 , it is not a grub of a beetle having a boring habit, 

 and liable to make a sound that might betray its 

 retreat, in seasons of the year when not torpid. 

 A caterpillar makes scarcely an appreciable noise, 

 even when spinning its cocoon, and when that is 

 finished it rests as quietly within as an Egyptian 

 mummy in its sarcophagus. 



There is no evidence that the downy woodpecker 

 ever makes a mistake ; it has some way of judging. 

 The squirrel does not waste time in cracking an 

 empty nut. There is no reason to believe that 

 this bird ever makes holes through these scales 

 merely for pastime, or for any other purpose ex- 

 cept for food. He knows before he begins that 

 if he works through, just in that spot, he will 

 find a dainty morsel at the bottom of it, as 

 delicious to him as the meat of the nut is to the 

 squirrel. But how does he know? By sounding 

 — tap, tap, tap, just as the physician learns the 

 condition of the lungs of his patient by what he 

 calls percussion.' The bird uses his beak, gen- 

 erally three times in quick succession — sometimes 

 oftener; then tries another. Watch him. See 

 how ever and anon he will stop in his quick mo- 

 tions up and down, and give a few taps upon the 



° This description of the woodpecker's search for 

 food bears a remarkable resemblance to a forty- 

 years later ( 1905 ) account of a percussion process 

 (Perkussionsverfahren) by a German investigator. 

 Dr. Wilhelm Leisewitz. 



suspected scale, and then test another and another, 

 until the right sound is communicated to that 

 wonderful ear (pp. 116-7). 



Besides studying the downy woodpecker in 

 the field he examined the stomachs of three 

 of them. One contained a codling moth larva 

 and some beetles. Another held one beetle, 

 the heads of two codling moth larvce and of 

 three small borers.' The third contained 

 beetles and grubs unidentified. 



The black-capped chickadee was also found 

 to feed upon the codling moth. Three speci- 

 mens were examined, one having eaten eggs 

 of lepidoptera and beetles, another four seeds 

 and a number of ' pupae of very small beetles, 

 such as take shelter under moss and old bark 

 on trees,' while in the stomach of the third 

 were five larvce of the codling moth. 



One of these had been so recently taken, and 

 was so little mutilated, that it was easily identified. 

 The heads of the other four appeared identical 

 when examined with a pocket-glass; but when sub- 

 jected to the test of the microscope, there was no 

 possible room for doubt. The day had been dry 

 and windy, following a warm wet day and night; 

 and it is in just such weather that the bark of the 

 buttonwood, shellbark hickory, and other shaggy 

 trees, will be found curling out and falling oflf. 



I have never seen anything that would lead me 

 to believe that this minute bird makes the holes 

 in the scales of bark that lead directly to the 

 cocoons of these caterpillars; they are made by 

 the downy woodpecker, and probably by it alone. 

 The chick-a-dee most likely finds these worms only 

 or chiefly on such days as this, when the warping 

 of these scales exposes them to the prying eyes of 

 these busy little friends. This bird is one of the 

 guardians of the orchard; quick, active, always 

 on the alert; assuming any position; sometimes 

 hanging by one foot on the under side of the large 

 limbs, where these caterpillars rather prefer to 

 conceal themselves; and now proved to feed freely 

 upon the second in importance of the insect 

 enemies of our fruits. Let no one hereafter kill 

 a chick-a-dee without being made to feel that he 

 has done a most disgraceful deed (p. 120). 



In further proof of their good work he says : 



For several mornings in succession I noticed that 

 the piazza was strewn with the cocoons and broken 

 pupa cases of the caterpillars (species?) that were 

 so numerous in September; sweep them off, and 

 soon they would be there again. It was the work 



