TRANSACTIONS OF NORTHERN ILL. HORTICULTURAL SOCIETY. 313 



to excess, we can not doubt that if the agency of birds should cease, 

 every green thing on the face of the earth would be destroyed by the 

 numberless tribes of insects. 



This is the general view of the subject ; but when we come to look 

 at the matter more particularly, some striking and exceptional facts pre- 

 sent themselves. Though, as we have seen, birds present a sufficient 

 antagonism to insects in the state of nature, they fail to furnish an ade- 

 quate check to the excessive multiplication of insects which has been 

 induced, in certain cases, by human intervention. The extensive culti- 

 vation of certain grains, fruits and vegetables, has been followed by a 

 proportional, and sometimes much more than proportional, increase of 

 some of those species of insects which subsist upon them. But there 

 being no species of birds which are the special antagonists of these par- 

 ticular kinds of insects, there has been no corresponding increase of 

 insectivorous birds. Accordingly, we find that in reducing the numbers 

 of many of those species of insects which are most injurious to the farmer 

 and horticulturist, birds afford so little aid that, in the practical treat- 

 ment of the subject, they may as well be thrown wholly out of account ; 

 whilst in the case of others, they furnish us with a partial but inadetjuate 

 assistance. In the last category are to be placed some of the exposed leaf- 

 eating caterpillars, such as the tent caterpillar and the canker worm, which 

 have been known, in particular localities, to have their numbers materially 

 reduced by certain species of birds. But if we take such examples as the 

 chinch bug, the Colorado potato beetle, the plum curculio, the Hessian 

 fly and the bark louse, we shall find that so far from feeding largely upon 

 any of these insects, birds scarcely touch them. The Hessian fly is too 

 small to be sought after by birds as a means of subsistence ; although a 

 similar insect, the wheat midge, is stated by Dr. Fitch to be sometimes 

 devoured to a considerable extent, whilst in the larvae state, by the black- 

 capped yellow bird, or American goldfinch. The bark louse is still more 

 minute, besides being protected by a scale which is scarcely distinguish- 

 able from the bark of the tree. The curculio is also probably protected, 

 to a great extent, from destruction by birds, by its resemblance to the 

 small knots and buds on the plum and peach trees. It is true, nature has 

 given to birds very sharp eyes to enable them to detect their insect prey, 

 but it is equally true that she has also endowed insects with the power of 

 mimicry, ai)parently for the express j)urpose of protecting them from their 

 feathered enemies. And in j^oint of fact, I believe birds have not been 

 known to frequent, in increased numbers, the plum and peach orchards 

 of the South, for the jjurpose of feeding upon the curculios with whi( h 

 they are so abundantly infested. Myriads of borers are undoubtedly 

 destroyed by woodpeckers, especially those which live under the bark, or 

 in rotten wood ; but the worst of them, like the round-headed borer of 

 the apple tree, penetrate so deejjly into the solid wood, at least in the 

 later stages of their existen( e, that even the woodpeckers cannot reach 

 them. With respect to the chinch bug and the Colorado beetle, they 

 seem to be absolutely repugnant to all kinds of birds, with i)erhaps a few 

 occasional exceptions, which, however, are not very well authenticated. 



