132 



TUANSACTIONS OF THE ILLINOIS 



It should be noted that eight of these birds were shot in and around 

 gardens ; but I do not think this an unfair ratio, as probably more than 

 half the species are gathered in such situations at this time. 



In August his case is somewhat more hopeful. Judging from the five 

 specimens obtained in this month, he returns to his caterpillars (but also 

 remembers his carabidse), begins his autumn work on grasshoppers, and 

 eats a diminished amount of fruit. Curculios and wire-worms were also 

 eaten to some extent, but not enough to incline the balance very decidedly 

 in favor of the birds. A small margin of profit may, perhaps, be ascribed 

 to his operations in this month. 



I found, on collecting the stomachs of these birds, that for one reason 

 and another we had none taken in September and October, and conse- 

 quently I can only surmise that during these months their habits gradually 

 improve with the disappearance of the cherries, the picking of the grapes 

 and the multiplication of the grasshoppers. Other observers report this 

 to be the case, and my own notes make it seem likely. 



Taking, now, the whole record for the six months from April 

 to August inclusive, I find that seventy-eight per cent, of the food 

 was insects and twenty-eight per cent, fruit, spiders and myriapods 

 making the other two per cent. Twelve per cent, were caterpillars 

 and seven per cent. Harpalincz. I may overestimate the value of 

 these predaceous beetles, but to my judgment these seven per cent, would 

 have saved much more than the twelve per cent, of caterpillars would 

 have destroyed.* Then we have six-and-one-half per cent, of injurious 

 beetles (including two-and-one-half per cent, of curculios), eight 

 per cent, of oethoptera and one-and-one-half per cent, of injurious 

 myriapods — sixteen per cent, in all — to offset twenty-eight per cent, 

 of fruit, the other elements about balancing each other. I there- 

 fore conclude that these forty-one robins taken together had certainly 

 done, just previous to the time of their demise, fully as much harm as 

 good, as far as we can judge from the contents of their stomachs. Farther 

 than this I do not intend to go at present, except to recall the mitigating 

 considerations that I have already mentioned. Luckily I am not required 

 to render positive judgment until I am satisfied with the evidence. 



In fact, the case is a much more difficult one than I supposed when 

 I collected this material, as there has been no suspicion hitherto that the 

 robin ate any unusual number of Harpalince, previous investigations of 

 this subject not having been definite and detailed enough to detect this 

 fact. It is his apparent preference for these predaceous beetles which 

 threatens to turn the scale against him, and so far complicates the question 

 that no positive conclusion can be reached this season. Temporarily we 



*Although most of these caterpillars were indeterminable, by far the larger part of 

 them were feeding on endogenous foliage — presumably grass — a fact easily demon- 

 strated by the presence, in the bird's stomach, of the peculiar similar fragments of leaves 

 escaped from the intestines of the half-digested caterpillars. The appearance of these 

 fragments is very characteristic, and is alone enough to indicate the presence of cater- 

 pillars in the food. 



