48 FOOD HABITS OF THE GROSBEAKS. 
tato beetle in many patches it patrolled. Mr. W. F. Bundy, who 
was among the earliest to write upon the subject, says: 
I noticed last summer that great numbers of the Colorado potato beetles were 
destroyed by the rosebreasted grosbeak. * * * They were so abundant in 
this region [Jefferson, Wis.] * * * as to hold in check the vast army of 
these ravagers of the potato crop. 
The beetles are attacked as soon as they emerge from their winter 
quarters, according to Mr. J. 8. Cook. of northern Illinois, who says: 
I have seen them so gorge themselves with these beetles that they were 
scarcely able to fly. I have investigated in the spring, when the beetles first 
came out of the ground, and was unable to find a single one after following 
these birds. 
Further testimony to the value of the bird is given by Prof. 
F. E. L. Beal“ who watched the grosbeaks and their young feeding 
upon the potato bugs in his garden at Ames, Iowa: 
When a careful inspection was made a few days later not a beetle, old or 
young, could be found; the birds had swept them from the field and saved the 
potatoes. 
Comparison of the dates of the first appearance of the Colorado 
beetle with the earliest records when the rose-breasted grosbeak fed 
upon it shows that from six to ten years passed before the bird com- 
monly began to prey upon the insect. Even after the lapse of so 
much time it was one of the first enemies of the beetle noted and by 
far the most important among birds. 
The results of stomach examinations fully corroborate the testi- 
mony of field observers as to the extent to which the rosebreast 
feeds upon this beetle. Forty-three. or almost one-fourth of the birds 
examined, fed upon the potato beetle to such an extent that the in- 
sect makes up 9.05 percent of the subsistence of the entire number 
and nearly 35 percent of that of the individuals eating it. The 
significance of these figures will be better appreciated when it is 
considered that the potato beetle probably was not obtainable by 
many of the grosbeaks, and furthermore, that it is very unusual for 
birds to prey so extensively upon a single kind of insect, or even on 
the species collectively of a whole group. Such concentration of 
attack of a common bird upon a single species of insect, however 
numerous. can not but have a restraining influence on its numbers. 
The beetle is fed upon from May to September and both larve and 
adults are devoured, 10 to 14 being found in single stomachs. By 
feeding upon the larve the rosebreast directly benefits the potato 
plants, and by destroying adults the increase of the species is checked. 
@ Am, Nat., IX, 1875, p. 375. ‘ 
>Trans. Il. Hort. Soc. 87 (1903), 1904, pp. 331-332. 
¢U. 8S. Dept. Agr., Farmers’ Bul, 54, 1904, p. 35. 
