104 The Food of Birch. 



cent, each of Arachnida and Myriapoda are the remaining 

 trivial details. 



Aug u st . 



This month is represented by twenty birds, all shot at 

 Normal,* at repeated intervals from the fourth to the 

 thirtieth. With the disappearance of blackberries, the food 

 of this bird returns substantially to the status of June. 

 Insects increase again to forty-three per cent, and fruits 

 fall to fifty-six. Ants remain at the usual point of insig- 

 nificance, caterpillars rise again to seventeen per cent., 

 about two-thirds of them Noctuidae. Coleoptera figure at 

 seven per cent., only two percent, being Carabidse, Rhyn- 

 cophora rise to four per cent., eaten by nine of the birds; 

 and, except a stray Nepa picked up by one robin, Hemip- 

 tera appear in trifiing quantity. Crickets and grasshop- 

 pers are more abundant, amounting to ten per cent, of the 

 food. 



The cherries made forty-four parts of the food of the 

 month, eaten by fourteen of the birds, hut tioo-thirds of these 

 cherries were wild. Tame grapes make three per cent, of the 

 food, berries of the mountain-ash about four per cent., and 

 blackberries from the woods not far from five per cent. 



Sep temher. 



Twelve birds, all but one shot at Normal September 

 25th, and that one at Aurora on the 13th, show no more 

 remarkable peculiarity than the substitution of ants for 

 most of the caterpillars, the former composing now fifteen 

 per cent, of the food, and the latter but five. The ants 

 were largely winged, but of different species from those 

 taken most freely in June.f The Oarabidae of this month 

 were chiefly larvae. Among the Hemiptera (three per 

 cent. ) were found Morinidea lugens and Cmnus delius. No 



*The general cessation of taxidermist's field work in midsummer 

 has prevented the supply of any material for this month and the preced- 

 ing, except that obtained by ourselves in McLean county. 



fExamining the tables of food of the bluebird, brown thrush and rob- 

 in, I find throughout a curious inverse relation between the ratios of 

 ants and caterpillars, the latter falling away in June to about the same 

 degree that ants increase during the time of their most conspicuous ac- 

 tivity. I cannot even guess why ants should thus replace caterpillars in 

 the food. 



