P. sylvestris in Britain is liable to many insect depredations: the pine-chafer, Hylurgus piniperda, is destructive in some places, the larva of this beetle feeding on the young succulent shoots, especially in young plantations; Hylobius abietis, the fir-weevil, eats away the bark, and numerous lepidopterous larvae devour the leaves; the pine-sawfly is also injurious in some seasons; the removal of all dead branches from the trees and from the ground beneath them is recommended, as most of these insects lay their eggs among the decaying bark and dead leaves.
Such cases are the habits of " shamming dead " and the combined posturing and colour peculiarities of certain caterpillars (Lepidopterous larvae) which cause them to resemble dead twigs or similar surrounding objects.
As a commercial product spider-silk has been found to be equal, if not superior, to the best silk spun by lepidopterous larvae; but the cannibalistic propensities of spiders, making it impossible to keep more than one in a single receptacle, coupled with the difficulty of getting them to spin freely in a confined space, have hitherto prevented the silk being used on any extensive scale for textile fabrics.
Lepidopterous enemies are numerous all over the world.
Sugar-canes suffer from the sugar cane borer (Diatioca sacchari) in the West Indies; tobacco from the larvae of hawk moths (Sphingidae) in America; corn and grass from various Lepidopterous pests all over the world.