estable larva had the unpleasant
fashion of lowering itself by a long silken thread from the shade
trees then so abundant in that beautiful city. The spanworms traveling
around over the clothing of the passersby were so objectionable to
everybody that it was with greatest delight that Philadelphia heard
of the new birds which ate the pest. One wonders why some
ornithologist did not look at the bird long enough to see that it had
the sort of a bill characteristic of birds that eat seeds. It is true
that most birds feed their young on insects, hence there is a time
when any bird is apt to be insectivorous. But the structure of the
sparrow's bill, like that of all finches, should have warned these
bird-lovers that the sparrow was not to be depended upon to earn his
living by catching worms. It is easy, however, to be wise after the
event. Philadelphia believed she was engaging in a particularly
advanced movement when she imported from England one thousand English
sparrows, nearly as many as were liberated by all other cities
together. These birds were turned loose among the shady streets and
wide spreading parks of the City of Brotherly Love.

It is a serious matter lightly to disturb the balance of nature by the
introduction of a new species. It is true that the sparrow did eat
some spanworms and for a while enthusiastic bird-lovers hoped that
here was the solution of the difficulty. Philadelphians will also
remember that, with the spanworm removed from competition, the tussock
moth, whose caterpillar carries on his back a series of yellow, red,
and black paint brushes, at once become the permanent parasite of the
long-suffering shade trees. This caterpillar is covered with bristling
hairs, very closely set. Almost any bird objects to hair in his
victuals; and this particular larva has hair more than ordinarily
objectionable, for it irritates wherever it pricks the sensitive skin.
This coating seems to protect the caterpillar from the sparrow, with
the result that Philadelphia's trees were soon nearly defoliated by
this comparatively new pest, worse than the spanworm. With the paving
of the city's highways and the consequent shutting off of the air from
the roots, the trees have largely disappeared from the streets of
Philadelphia. With them have gone a fair portion of the tussock worms,
but the sparrow holds his own. Here is a new bird in the field, and
the struggle for existence on the part of every other kind of bird i