42 TRANSACTIONS OF THE ILLINOIS 



6. Coleoptera, considered in the mass, are to be reckoned injurious. 

 Cicindelidae, larabid^e, lampyridtE and coccinellidse are beneficial. Cur- 

 culionidce, cerambycidce, and some Meloidae, the tetramerous beetles, 

 leaf-shafers and hard-winged serricornes, are especially injurious. 



7. Hemiptera are injurious, on the whole. The aquatic hemiptera, 

 however, are neutral, and reduvidse, arma and syrtis, are beneficial. 



8. Orthoptera may be set down as injurious, except perhaps Blatti- 

 dze. Those species which are not now especially hurtful would many of 

 them become so, if their increase were unrestrained. 



9. A bird living on small Neuroptera is of suspicious character. It 

 may eat lace-wings. Otherwise, a neuropterous diet is allowable. 



10. Myriapodse are, on the whole, beneficial — Chilopodas especially 

 so; Chilognath^e neutral. 



11. Spiders are beneficial, and birds eating them largely are to be 

 watched. Phalangidas (harvest-men) are especially to be protected. 



In addition to these principles, I drew up a sort of a standard of 

 values — a working table to be used in determining the relative weight to 

 be given to each class of facts observed. As this is somewhat compli- 

 cated, I will give only a single item to illustrate its character and use. I 

 assumed that 50 per cent, of the beetles eaten by birds are injurious ; 25 

 per cent, are beneficial, and 25 per cent, neutral. Therefore, whenever 

 the material in a bird's stomach was of such a character that I could rec- 

 ognize coleoptera, but could not tell the genus, or even the family, I 

 credited this particular bird with 50 per cent, of benefit, and charged it 

 with 25 per cent, of injury. The other groups of insects are similarly 

 treated. 



More definite determinations of the material examined, than those 

 implied above, are often impossible, and to use only such matter as can 

 be specifically recognized would cause great waste. Besides, I doubt if a 

 classification within narrower limits is necessary for our purpose. We 

 must not suppose that a bird stops to study the markings on the elytra of 

 a beetle, or to count the joints in its antinnae, before concluding to swallow 

 it; and a bird that takes one species freely will be very likely to appro- 

 priate allied species or congeners of similar habitat. 



It will be understood that the percentages of the following table are 

 not so statistically accurate as their form might imply. They simply 

 afford a brief and definite expression of my o-wn Judgment in the matter, 

 after the most detailed and careful study I have been able to make. 

 Doubtless I shall make myself perfectly understood when I say that I have 

 used, upon a much more complicated subject, the same marking system, 

 which is generally employed by teachers as a means of recording their 

 estimates of their pupils' work ; and the percentages which I shall now 

 read to you correspond to the term-averages which appear on the reports 

 of your schools. I don't know that any better method has ever been 

 devised for making the closest possible approximation to the truth in a 



