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IOWA ACADEMY OF SCIENCE 
status of these birds it is easy enough, to estimate in dollars and cents 
their depredations on fruit ; but it is impossible to state in similar terms 
the value of their work in destroying noxious insects because we deal 
here not only with the actual insects destroyed with but numerous other 
generations which would follow. 
Comparing these results with those of the previous report, we find that 
while the two studies were made in different localities, and during two 
quite dissimilar seasons, the results compare very favorably. In the 
former report we find a total of 1,260 morsels of food consumed. 425 
of these were mayflies ; 247 grasshoppers ; 103 cutworms ; 38 beetles and 
22 larvae, practically all of both being maybeetles; and 425 of various 
forms in small numbers, including 237 moths of various species. The 
two greatest discrepancies shown by a comparison of Table III of the 
previous report and Table I. of the present article are first, the large 
number of mayflies and moths consumed by the first brood studied and 
their total absence from the list of insects fed to the last brood and sec- 
ond, the absence of fruit in the first table and its presence in the latter. 
These facts will be discussed in the next paragraph. Selecting from the 
previous study the data on the three forms of insects most numerous in 
the present data, viz., grasshoppers, maybeetles, and cutworms, we find 
the three forms total 410 out of 1,260, or 32.54%. Mayflies form 33.73% 
of the total and the remaining 33.73% consists of moths and miscel- 
laneous species. From the data furnished by these two studies, it seems 
that these three forms mentioned above furnish a considerable percentage 
of the nestling food of the species. No definite figures can be given as 
the percentages will vary somewhat in individual birds and will also 
fluctuate from day to day in the food of the same individual. This 
fluctuation will depend on two factors ; first, on the number of indi- 
viduals of each species of insects that are in the immediate vicinity of 
the nest; and second, on the availability of other food supply. 
There are two general facts that may be stated from the data obtained 
which have some bearing on the economic status of the species. 
First, a great number of species of insects are acceptable to the brown 
thrasher as food. A glance at the two tables previously mentioned will 
be sufficient to demonstrate this fact and further study would undoubt- 
edly greatly extend the list. 
Second, the birds easily adapt themselves to varying conditions in the 
food supply and so act as a check on different species of insects. For 
example at Okoboji in 1911 the mayflies were present in great numbers 
and the food of the brood studied consisted of over 33% of this form. 
Grasshoppers were numerous and formed 20% of the food and 19% 
