REPORT ON INSECT FOOD. 57 



It appears from this table that the average quantity of insect material 

 in these 909 stomachs was almost 24 percent. A moment's examina- 

 tion of the table shows, however, that the number of stomachs exam- 

 ined in different months is very unequal, and also that the percentage 

 varies widely according to season. The average percentage represents 

 the proportion of insects to the whole stomach contents, but from 7 to 

 10 percent of the stomach contents is sand or gravel. Throwing out 

 this mineral element, it appears that on the average 26.17 percent of 

 the Crow's food for the year is made up of insects. In the same way it 

 is found that even in January, when the smallest proportion is eaten, 

 insects form almost 3 percent (2.71) of the food, while the maximum 

 is reached in April with almost 53 percent (52.75). In May, insects 

 constitute about 49 percent (48.97) of the food, and in June about 41J 

 percent. 



During the months of May and June 529 stomachs were collected; 

 insects formed 46.7 percent of all food in these stomachs. Since these 

 two months cover the larger part of the time when Crows are rearing 

 young, this large proportion of insect food perhaps is not surprising, 

 especially as 396 stomachs were those of young Crows taken from the 

 nest. The insect food in the stomachs of these nestlings averaged 49.6 

 per cent, while the average amount in the stomachs of 120 adult Crows 

 taken during May and June was only 36.4 percent. This shows con- 

 clusively that young Crows while in the nest eat more insects than the 

 adults, the difference in this case amounting to more than 13 percent 

 of the entire food; or, to put the matter in another form, nestling 

 Crows eat at least one-third more insects than the adults. It is of 

 great importance, however, that the character of this insect food be 

 carefully determined, so that we may know positively whether its con- 

 sumption is or is not of benefit to the agriculturist. Fortunately, this 

 has been done. After the preliminary examination of the contents of 

 each stomach and the determination of the percentages of the several 

 kinds of food contained the insect material was referred to Prof. C. V. 

 Riley, then chief of the division of entomology, under whose direction 

 it was thoroughly studied by Mr. E. A. Schwarz. The following- 

 reports contain the results of this examination : 



Report on the Insect Food of the Crow. 



By E. A. Schwarz, Assistant, Division of Entomology. 



The examination of the contents of about 600 stomachs of Crows 1 

 submitted by Dr. C. Hart Merriam to the division of entomology was 



1 The insect contents of 801 Crow stomachs were submitted to Professor Riley for 

 examination, but in several cases where many stomachs were collected on the same 

 day and at the same place, under precisely similar circumstances, it was not thought 

 necessary that all should be examined critically. In such cases half or more were 

 thoroughly examined and the results tabulated, while the remainder were passed 

 over with a simple inspection. — W. B. B, 



