108 USEFUL BIRDS. 
and probably drag the young larve out of the smaller 
twigs. 
It is extremely difficult and expensive to raise forest trees 
in regions where there are no arboreal birds. The larve 
of several large nocturnal moths are among the most 
destructive insects known. Mons. Trouvelot’s statement 
(pp. 80, 31) regarding the quantity of food eaten by the 
larva of polyphemus illustrates the power for harm that 
these creatures possess. The larve of Platysamia cecropia 
and Actias luna are so gigantic and their rate of increase is 
so great that they constitute one of the gravest dangers that 
constantly menace our woodlands, yet we never hear of any 
serious injury done by them in Massachusetts. Indeed, such 
species, although large and conspicuous, are not often seen 
except by entomologists and collectors of insects, who know 
their haunts and habits. The main reason for their compar- 
ative scarcity is indicated by Trouvelot’s experience in rear- 
ing the larve of Telea polyphemus, the “ American silkworm.” 
He had a tract of about five acres enclosed, and covered with 
netting for the protection of these caterpillars. The vegeta- 
tion on this land as I saw it years afterward was largely scrub 
oak and whortleberry or huckleberry bushes. Trouvelot says 
that when he began rearing silkworms the bushes were of 
about five years’ growth, and it seemed as if there would be very 
little to do after the place was enclosed and the insects put 
in; but he found that most of his time was occupied in de- 
fending his treasures against the birds. The smaller of these 
would push through the meshes or get under the edges, while 
the larger ones would find some hole by which they could 
enter. He says that he was obliged to chase them “all the 
day long,” as when he was pursuing them on one side they 
would fly to the other and quietly feed until he reappeared. 
* Birds,” he says, “are the greatest foes of silkworms, espe- 
cially the Thrushes, Catbirds, and Orioles.” He believes it 
probable that in a state of nature ninety-five per cent. of 
the silkworms become the prey of these feathered insect 
hunters.” 
Samuels tells us that Trouvelot was obliged, in self-defence, 
1 American Naturalist, Vol. 1, p. 143. * Tbid., p. 89. 
