﻿12 BULLETIN 1355, tJ. S. DEPARTMENT OF AGRICULTURE 



varying proportions, amount to only 0.47 per cent and may be dis- 

 regarded for practical purposes. 



Hymenovtera. — Approximately 14 per cent of the annual sub- 

 sistence of the Philadelphia vireo is composed of wasps, bees, and 

 related insects. Here are to be found some of the most beneficial of 

 all insects, the parasitic ichneumon fhes and the minute chalcids. 

 On the other hand, the kinds of ants eaten are usually injurious, 

 especially the large, black, carpenter ants {Camponotus lierculeanus) , 

 and even if some of them do no direct damage they are indirectly 

 injurious in fostering plant lice. At times the birds fill their stomachs 

 with many individuals of the same species; for instance, one bird had 

 eaten 20 individuals of a certain ant (ApJiaenogaster) ; another, 10 

 sawflies (Tenthredinidae) ; and a third, 15 sawfly larvae. In its 

 economic status the Philadelphia vireo, so far as hymenopterans are 

 concerned, must be considered beneficial in that the injurious insects 

 captured outnumber by far the beneficial forms. 



Diptera. — In the 84 stomachs examined the remains of flies were 

 detected in 36, or more than a third. In 19 of these the flies were of 

 the midge family ( Chironomidae) , and in some, midges made up 

 nearly the entire contents. Flies form 11.76 per cent of the food. 

 This item includes both beneficial and injurious forms and may be 

 listed as economically neutral. 



Hemiptera. — True bugs make up 10.46 per cent of the annual food 

 of this vireo, 1.67 per cent being composed of stink-bugs (Pentato- 

 midae). These are large, flat insects, and the majority are injurious. 

 One group, including the species of the genus Podisus, are, because 

 of their predacious habits, reckoned among the beneficial forms. 

 Fortunately, members of this genus are rarely found in the stomachs 

 of the Philadelphia vireo, hence the stink-bugs in general may be 

 placed on the credit side. Assassin bugs (Reduviidae) , another 

 group of beneficial bugs, are entirely lacking in these stomachs, so 

 that on the whole the true bugs eaten are to the credit of the bird. 



Other insects. — The remainder of the insect food of this bird, 

 amounting to but 1.14 per cent, has little or no economic significance. 

 It is made up of a few neuropteroid insects, together with fragments 

 so comminuted that further determination was impossible. 



Spiders. — It is not surprising that spiders, so common on the leaves 

 and twigs of bushes and trees, should have been taken by 34 of these 

 birds to the extent of 4.34 per cent of their food. Once the kind 

 eaten proved to be a daddy longlegs or harvestman (Phalangidae) , 

 and 10 times the fragments were readily determined as of the family 

 of jumping spiders (Attidae). In the other cases, however, it was 

 impossible to decide the kind of spiders represented. Spiders are 

 probably all beneficial in a small degree, but the eating of a few 

 should not count heavily against an insectivorous bird. 



VEGETABLE FOOD 



Lack of stomach material of the Philadelphia vireo, representing 

 early spring or late fall, makes it impossible to show exactly how the 

 relation between animal and vegetable food varies with the season. 

 As the new crop of wild fruits develops, however, the birds are 

 attracted to it, and in September this item forms 18.71 per cent of 

 the diet. Among fruits identified were dogwood berries, taken four 

 times, while bayberries {Myrica carolinensis) , wild rose hips (Rosa), 



