20 THE RELATION OF BPARBOW8 TO AGRICULTURE. 
occasionally includes Emails or millipedes; insects — mainly grasshop- 
perSj beel les, and caterpillars — constitute more than nine-tenths. The 
table food is composed almost entirely of seeds, although it also 
comprises a small quantity of fruit. 
rOOD MUTUAL IN EFFECT OX AGRICULTURE. 
The neutral pari of this food is made up principally of certain 
insects, spiders and snails, a small amount of wild fruit, and some 
seeds of useless plants. Insects form about four-fifths of the animal 
matter of the neutral part, comprising ants and certain kinds of flies 
and beetles. The flies, which are usually adult insects, but some- 
times larva 1 , include midges (Chironomidse), flies related to the house- 
fly (Muscidae), .March-flies ( Bibionidae), and crane-flies (Tipulidm). 
These insects never amount to 1 percent of the volume of the entire 
food of any species of sparrow for the whole year. May-flies (Ephem- 
eridse), emerging from the water by the million, are preyed on by the 
sparrows that dwell in the immediate 
vicinity of streams or ponds. Ants sel- 
dom equal 2 percent of the volume of the 
year's food. Both typical ants (Formi- 
cida?) and myrmicids (Myrmicidse) are 
taken. Such ants as Formica fusca and 
F. subsericia, Lasius, Myrmica^ and Te- 
tramorium are frequently selected. They 
are often eaten while yet in the winged 
state and are then caught in the air. 
Beetles of little or no economic impor- 
F ' «, oa^uy^l'l ^X:T """•<• «™int to from 3 to 5 pereenl of 
the total volume of the food for the en- 
tire year. r l nese are for the most part dung-feeding species belong- 
ing to the genera Aphodius (see rig. 11), AUznius, Onthophagus, and 
Wish r. They are often found by hundreds in cow droppings in 
pastures. 
The remainder of the neutral pari of the food is made up of spiders 
and snails. Spiders, though predatory, have not as yet been classed 
as useful, because, as already stated, as a group they seem to destroy 
about as many beneficial as injurious insects. The kind most fre- 
quently eaten by sparrows are the running ground-spiders, which, 
though probably more useful than harmful, are of too little importance 
to be classed otherwise than as neutral. They constitute 1 to 3 per- 
cent Of the food. A few snails are eaten. These are as a rule not 
injurious; and though an exception should be made of the pond snail 
( Ldmna " ). which acts as intermediate host to the liver fluke, a pesl to 
she.-p raisers, probably very few if any of these are included among the 
Small number of snails actually eaten, and they may be disregarded. 
