INSECT FOOD. 41 



(Melanohraam) , of which at any tmie during the first part of September, 

 1896, a dozen could have been collected within a few minutes. Field 

 sparrows and probably other birds consumed them freely, though as 

 a rule parasitic Hymenoptera are eaten only in small numbers. 



Many of these useful species appear too late in the season to be of 

 much effect. An attempt was made to measure the evil effects of their 

 destruction by observing how far they were parasitizing abundant 

 insect pests, but conditions were unfavorable and adequate results 

 were not obtained. The white grub of the Maj^ -beetle was not present 

 in numbers sufficient to furnish evidence. The tobacco worm was par- 

 asitized by braconids to some extent, but even at the time of greatest 

 activity (August, 1898) only one-tenth of 1 percent of the worms were 

 attacked. The question, then, of the degree to which birds offend by 

 preying on these H^mienoptera remains, so far as Marshall Hall is 

 concerned, a doubtful one, especially since most of the species 

 destroyed are not known to be effective parasites. 



SUMMARY. 



Considering the insect food of the 615 native birds collectively, we 

 find that the birds were most insectivorous in May, when somewhat 

 more than 90 percent of their food was insects, and that natural^ they 

 took the fewest insects in the coldest weather. During the blizzard of 

 February, 1900, however, insects constituted 12 percent of the diet 

 of the 37 birds collected. Throughout the entire time of observation 

 insects and their allies, including a small percentage of spiders and 

 other invertebrates, amounted to 60.11 percent of the total volume of 

 food. They are distributed as follows: 



Proportion of insects and their allies in food of birds examined. 



Percent. 



White ants ,... 1.07 



Bugs 3. 63 



May-flies 6. 51 



Ants and other Hymenoptera 9. 64 



Caterpillars, with a few adult Lepidoptera 7. 80 



Grasshoppers and a few crickets 4.11 



Beetles 18.62 



Miscellaneous insects 3. 72 



Spiders 4. 48 



Miscellaneous invertebrates, mainly Crustacea, snails, and myria- 

 pods 83 



Total.... 60.41 



The bugs consisted both of Heteroptera and Homoptera. The 

 Heteroptera included such forms as Podisiis^ JEuschistus, Tricliopepla 

 seniivittata^ Sinea dladema^ Thyanta custator^ Hymenarcys nervosa^ 

 Metapodi'us femoratus^ Nezara hilaris^ Corizus^ Coriscus^ Corhneldena^ 

 Prionidus^ Alydus pilosulus, and Alydus eurinus. The Homoptera 



