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BULLETIN 1355, U. S. DEPARTMENT OF AGRICTJLTUKE 



Orthoptera. — No other species of vireo of which the food habits 

 are known takes so large a quantity of such bulky insects as grass- 

 hoppers, locusts, and the like. Though the present species is one 

 of the smallest in size, it includes in its diet for July enough of the 

 orthopteroids to make 34.88 per cent of that month's food. This 

 form of food is essentially a summer type, none being taken in May, 

 a considerable quantity in June, and 21.87 per cent in August. The 

 average percentage for the summer months is 18.52. 



Lepidoptera. — About one-fifth (20.63 per cent) of the subsistence 

 of the Bell vireos during the summer is made up of caterpillars, and 

 of adult moths and butterflies, and their eggs. As the last-named 

 items are rarely found in a stomach, the figures given refer mainly 

 to the first two. Caterpillars do not become an important factor in 

 the economy of the birds before June, although a few (1.67 per cent) 

 are eaten in May; in each of the months July and August the con- 

 sumption amounts to about 25 per cent, and the average for the 



Fig. 9. — ^Yearly- summary of the various items in the food of the Bell vireos ( Vireo belli, suhspp.), based on. 

 the analysis of the contents of 52 stomachs 



four months is 15.89 per cent. Lepidopterans in other stages make 

 up 4.74 per cent of the food, the consumption being heaviest in July 

 (11.07 per cent). 



Coleoptera. — Beetles of all kinds make up 15.26 per cent of th& 

 summer food of the Bell vireos. Ladybird beetles are taken in 

 moderate numbers and form 2.19 per cent of the total food. Weevils 

 (6.09 per cent) and leaf beetles (3.98 per cent) account for the most of 

 remainder of the coleopterous food. 



Hymenoptera. — Hymenopterans of all sorts (bees, wasps, etc.) 

 amount to 6.44 per cent of the total diet during the summer months. 

 The increase in consumption is at first slight. May and June being 

 represented by 2.33 and 3.2 per cent, respectively. In July a sharp 

 rise is noted to the maximum of 12.83 per cent; in August it is only 

 7.38. The evidence at hand probably gives a fairly correct view of 

 the facts. 



