I40 TRAJSrSACTIONS OF THE ILLINOIS 



No thorough discussion of this sort can be attempted, since I have 

 studied no other family with equal care, and can consequently make 

 scarcely any comparisons. I will, therefore, content myself with a few 

 general statements. From the large number of individuals here taken 

 into account, the conclusions given are much less likely to be disturbed 

 hereafter than those relating to species. 



The food of the family, taken as a whole, I find to consist of insects, 

 seventy-three per cent.; myriapods, five per cent.; and fruits, twenty per 

 cent.; the remaining two per cent, consisting of moUusks, spiders, etc. 

 The most important insect elements are ants, nine per cent.; caterpillars, 

 fourteen per cent.; carabidee, seven per cent.; curculios, two-and-one- 

 fourth per cent.; other injurious beetles, six per cent.; and oethoptera, 

 five per cent. One crude comparison of these birds with the others 

 studied is worth making, as an additional evidence that the thrushes are 

 inordinately destructive to carabidae. Of the one hundred and forty- 

 nine thrushes examined, seventy-one had eaten carabidse (nearly forty- 

 eight per cent.), while of one hundred and ninety-four other insect-eating 

 birds studied only nine had eaten these predaceous beetles — less than 

 five per cent. 



I confess to you, gentlemen, that, taking these figures as our guide, 

 I am unable, with my present knowledge of economical entomology, to 

 attach any great economical value to the Thrush Family. Please notice, 

 however, that I give you this opinion merely as the point towards which 

 my studies are now tending, and not as by any means a final conclusion. 

 It will take a good deal more of tedious and difficult labor on this subject 

 to give any one the right to use a positive "yes" or "no." 



Most of all we must learn what these birds do in great emergencies, 

 when the insect hosts arise against us in immense rebellion, and threaten 

 the whole wealth and business of the State. We know that this standing 

 army of birds costs us something in time of peace. We have just learned 

 that it is given to lawless and murderous forays across the border, plun- 

 dering our own allies mercilessly and weakening them for our defense; 

 but we must not, therefore, commit the folly of condemning our soldiery 

 until we know how they behave in time of war. Doubtless we could well 

 afford them better rations from our fruit-fields if we could repress their 

 foraging on our friends; and, possibly, we may be able finally to enlist a 

 better disciplined army in our service. We may find it worth while to 

 colonize some of the birds of Europe as we do its fishes. But it is not 

 impossible that we may, at some future time, find these thrushes banded 

 together in an invulnerable phalanx for the protection of our farms and 

 gardens against an otherwise overwhelming horde of insects. I would, 

 in short, treat this question with careful conservatism, remembering that 

 he who disturbs the delicate balance of Nature's adjustments is certain to 

 produce many and far-reaching effects which he cannot possibly foresee; 

 and that we should, therefore, venture to assume her prerogative only 

 when the evident good in prospect is sufficient certainly to compensate 

 for the possible evil. 



