﻿^0 BULLETIN" 1355, U. S. DEPABTMElsrT OF AGRICULTURE 



Coleoptera. — ^Considering the enormous numbers of beetles avail- 

 able, it is somewhat surprising that not more are eaten. The blue- 

 heads manage to seek out enough, however, to make up 13.51 per 

 cent of their entire diet. Of this, the ladybird beetles make up 4.88 

 per cent, or more than a third. It is certain that there are not a 

 third as many ladybird beetles as all other beetles combined; and thus 

 it must be considered that the blue-headed vireos, like the warbling, 

 either find these brilliantly colored forms in abundance in their envir- 

 onment or else make special search for them, a most undesirable habit 

 ^economically. Roughly, a second third of the total bulk is composed 

 of the metallic wood borers, the longicorns, and the click beetles. 

 The remaining portion includes, among others, the weevils, which 

 comprise 1.8 per cent of the food. 



Hymenoptera. — With the exception of the month of March, mis- 

 cellaneous hymenopterans were eaten in quantities varying from 1.75 

 per cent (in January) to 16.78 per cent (in May). Remains of no 

 very important insect pests were found among the fragments from 

 the stomachs, though several sawflies and ants were detected. The 

 average for hymenopterans eaten during the year was 6.86 per cent. 



Diptera. — Two-winged flies make up the comparatively small per- 

 centage of 4.29, or less than that of the single family of coccinellids 

 (ladybird beetles) , although flies are almost universally present. The 

 flies of the woods are in general of little importance, excepting the 

 bloodsucking forms; and as these are not often found in the stom- 

 achs, the economic importance of the dipterans in the food is slight. 



Other insects. — Among the insects eaten which do not belong in the 

 above classes are the stone flies, dragon flies, grasshoppers, crickets, 

 and locusts (6.56 per cent for the year) , In January this group is one 

 of the most important, making 21.76 per cent of the food. February 

 shows a slight decrease (18.38 per cent), and from then on the per- 

 centage varies from 1.24 in May to 7.5 in August. In general, this 

 group is of no more importance economicaUy than the dipterans. 



Other animal food. — Spiders run very evenly in the food of birds of 

 this species and are probably picked up whenever occasion offers. 

 With the exception of February, when they amount to but 0.18 per 

 cent, spiders are present in percentages varying from 1.51 to 5.55, 

 the last figure representing August. The average of 2.63 per cent may 

 be taken as a fair estimate of the quantity of this type of food eaten 

 by the blue-headed vireos. 



Snails are sometimes eaten, but so rarely that they are not to be 

 considered an essential part of the diet (yearly average, 0.25 per 

 cent) . 



VEGETABLE FOOD 



During the winter months vegetable food is of considerable impor- 

 tance in the diet of this bird. In January nearly a quarter of the 

 total was of vegetable origin (24.37 per cent) and in February less 

 than a tenth (9.81 per cent). From March to and including August 

 no trace of vegetable matter appeared in the food, but by November 

 it formed 4.44 per cent. For the most part it was in the form of 

 fleshy fruits, such as wild grape, dogwood, viburnum, and wax 

 myrtle. No cultivated fruit was identified, and it is practically 

 certain that none is eaten. 



