INSECT FOOD OF CUCKOOS. 9 
one of the nine stomachs examined by him. 1 These observations show 
that cuckoos do at times eat fruit, but the results of our investigation 
indicate that it is not their usual habit. 
The insect food of cuckoos consists of beetles, grasshoppers, cicadas, 
bugs, aiits, wasps, liies. caterpillars, and spiders, of which grasshoppers 
and caterpillars constitute more than three-fourths. The great majority 
of the insects found in the stomachs were harmful kinds. Caterpillars, 
katydids, and tree crickets are exactly the prey that cuckoos might 
be expected to secure from their peculiar method of hunting in foliage, 
while the large numbers of grasshoppers eaten furnish additional proof 
of the fact so often illustrated that birds are particularly fond of grass- 
hoppers, and that species not naturally ground feeders become so 
during the grasshopper season. 
It is a matter of common observation that cuckoos feed largely on 
caterpillars, and stomach investigations not only confirm this but show 
that unlike most other birds they eat freely of hairy and bristly species. 
ZSearly half of the cuckoo's food was found to be caterpillars. An 
attempt was made to obtain an approximate idea of the actual number 
in the stomachs by counting the heads and jaws, but in many cases 
this was nearly impossible, as many of the insects were very young and 
the jaws consequently minute. The result of this estimate, however, 
showed that no less than 2.771 caterpillars were contained in 129 
stomachs, or an average of more than 21 in each. If the whole num- 
ber of stomachs (155) is considered, the average is reduced to 18, and 
it is absolutely certain that this is much below the actual number. 
During May and June, when tent caterpillars are defoliating the fruit 
trees, these insects constitute half of the cuckoo's food. When cuckoos 
visit the nests of the tent caterpillars they apparently eat as many of 
the occupants as possible. Most of the stomachs that contained the 
larvae at all were filled with them, some having more than 100 indi- 
viduals. .Mr. Otto Lugger, formerly of the Department of Agricul- 
ture, examined one stomach which was so full that he concluded that 
the bird had devoured the whole colony, as there were several hun- 
dreds of these hairy caterpillars. 
Perhaps the most curious insects found in the cuckoo stomachs were 
the larvae of the Io moth. These caterpillars are thickly covered 
along the back and sides with spines growing from tubercles, which 
are not only very sharp but poisonous, and sting the hand quite 
severely when carelessly touched. Nevertheless, they were found in 
five stomachs, one of which contained seven, another three, and the 
others one each. 
It is noticeable that the larva^ of moths, particularly hawk-moths 
(Sphingid(v), are eaten much oftener than those of butterfiies. Whether 
this comes from preference and selection on the part of the bird or 
from the greater abundance and more conspicuous habits of the insects 
1 Birds of Pennsylvania, 2d ed., p. 161, 1890. 
