I 



INSECT FOOD OF CUCKOOS. 9 



one of the nine stomaclis examined by himJ 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, ants, wasps, flies, 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. 

 Nearly 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 

 larviB 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 i)here were several hun- 

 dreds of these hairy caterpillars. 



Perhaps the most curious insects found in the cuckoo stomachs were 

 the larvte of the lo 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 larvie of moths, particularly hawk-moths 

 {SpMngidce), are eaten much oftener than those of butterflies. 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 



Birds of Pennsylvauia, 2d ed., p. 161, 1890. 



