SWALLOWS. Oo" 
food, migrate in great numbers, and then are preyed upon by swal- 
lows, flycatchers, and other birds. The destructive cotton boll weevil 
is more or less active during the late summer and early fall months, 
and it has been learned that the swallows, as they pass through the 
cotton States on their way to their southern winter quarters, catch 
great numbers of them on the wing and so perform an exceedingly 
important service. Engraver beetles (Scolytide) have frequently 
been found in the stomachs of swallows. These insects live under 
bark, and generally are inaccessible to birds, except woodpeckers; 
periodically they migrate from the tree where hatched and matured 
to search for fresh pastures; at such times they are unprotected and 
fall easy prey to any fly-catching bird. Swallows are peculiarly 
adapted to capturing small insects in mid-air. While their bills are 
weak their mouths are wide, and their long wings enable them to fly 
swiftly and turn quickly, so that they sweep back and forth through 
a swarm of insects and gather them by hundreds. 
Seven species of swallows, with several subspecies, are commonly 
found within the limits of the United States. Their food habits 
vary but little. All seven species occur in California, and this num- 
ber includes one, the violet-green, that does not occur in the East. 
Besides the swallows whose food will be discussed in detail in the 
following pages, a few stomachs of the tree swallow (Jridoprocne 
bicolor), the western martin (Progne subis hesperia), and the bank 
swallow (Riparia riparia) have been examined, but the number is 
entirely too small to be used as a basis for general conclusions were 
it not for the fact that their contents agree in all essential points 
with those of the other swallows, of which a greater number were 
available for examination. In fact, it may be said of all the members 
of the swallow family that they subsist upon practically the same 
kind of food, with slight variation from month to month. It may 
be laid down as a general rule that the food of all American swal- 
lows is derived from the following orders of insects: Coleoptera, 
Hymenoptera, Hemiptera, and Diptera, with a few individuals from 
one or two other orders, and an occasional spider. So far as present 
investigation has shown, 90 percent of their animal food is from the 
four orders named above, but the relative proportion of each varies 
somewhat with the different species and seasons. With one notable 
exception * the swallows take so little vegetable food that it may be 
passed by as a negligible quantity, and much even of the httle-eaten 
is probably swallowed accidentally. ) 
After the above statements in relation to the food of the swallows, 
it is perhaps unnecessary to dwell upon the great value of these birds 
¢The tree swallow of the East (Jridoprocne bicolor) during its southern 
migration freely eats the berries of the bay-berry (Jlyricu carolinensis). 
