20 The Regulative Action of Birds upon Insect Oscillations. 
after subtracting the canker-worm ratio from the average of that 
order taken by the first group, differs by only three per cent, from 
the average taken by the second group. The discrepancy in the 
ratios of Coleoptera is not so easily explained, but is distributed 
among several genera of Scarabaeidae and the small scavenger 
beetles. The excess of these two orders is compensated princi- 
pally by diminished ratios of vegetation, which amount to only 
six per cent, in the birds shot in the orchard, and fifty-two per 
cent, among those taken through the country at large. Diptera and 
all the lower orders of insects as well as Arachnida and Myriapoda, 
are also omitted from the food of the orchard birds. 
Insects composed ninety-seven per cent, of the food of eighteen 
indigo birds ( Passerina cyanea) shot in the orchard, and but fifty- 
seven per cent, of the food of fifteen individuals taken elsewhere, 
the balance in both cases being seeds, chiefly Setaria, Polygonum 
and wheat. The excess of insects in the orchard specimens 
appears under Lepidoptera and Coleoptera, the former sixty-seven 
per cent., the latter twenty-nine, as compared with twenty-eight 
and nineteen per cent, respectively, in the other group. The 
Lepidoptera of the orchard birds are nearly all canker-worms, as 
are likewise ten per cent, of those taken by the specimens from 
various situations. The difference in the ratio of Coleoptera 
taken by the two groups was exactly compensated by the ten per 
cent, of Anomala binotata eaten in the orchard. The excess of 
caterpillars and beetles taken by the former group, is partly com- 
pensated also by the almost total disappearance of all other 
insects from the food. 
What, now, may we conclude, from the above data, respecting 
the influence of birds upon such entomological insurrections as 
are illustrated by the uprising of the canker-worms in Mr. Rob- 
ison’s orchard? 
Three facts stand out very clearly as results of these investiga- 
tions: 1. Birds of the most varied character and habits, migrant 
and resident, of all sizes, from the tiny wren to the bluejay, 
birds of the forest, garden and meadow, those of arboreal and 
those of terrestrial habit, were certainly either attracted or 
detained here by the bountiful supply of insect food, and were 
feeding freely upon the species most abundant. That thirty-five 
