Pine Sawflies
Under Lophyrus and Lyda will be found some general remarks on the Sawflies that belong to these genera. The species are all more or less hurtful to Conifers, but Lophyrus Pini is the one generally denoted by the name of Pine Sawfly. The insects are heavy-bodied, with four transparent wings, which often show a play of iridescent colours. In the male they reach about 1/2 in., and in the female about 3/4 in., in their expanse. The male is black. The female is pale yellowish-white, with black head, antennae, and breast; and the back between the wings, and a large patch on the abdomen, are black. The eggs are laid on the leaves, in slits made by the females. The larvae feed in company, eating the leaves from the tips downwards, and also gnawing the bark of the young twigs, and thus doing great damage to the Scotch Fir. They are usually light greenish-yellow in colour, more rarely pale yellow, or dark green above, and are sprinkled with minute black granules. The head is brown, with dark spots. When full-fed, the larvae crawl under moss and leaves, or into crevices, and spin oval cocoons, about 1/2 in. long, of very compact texture, and usually dull brown in colour.
The other Sawflies most injurious to Firs and to other Conifers in Britain, are the following: Lophyrus frutetorum, L. sertiferus (L. rufa), and L. virens; and of the genus Lyda the most hurtful are L. erythrocephatus, L. nemorum, and L. stellatus. In their general appearance and habits, they agree with Lophyrus Pini, differing only in minor details. It is unnecessary to enter into descriptions of the different species, since they are so much alike; the same means of destruction may be employed against all of them.
Remedies. Moss, loose bark, and other debris, amongst which the cocoons are spun, should be collected and burned. The larvae may be hand-picked from the branches, or crushed on them, with good results. Naphtha and solutions of Hellebore have also been directed upon them successfully. They may be shaken from larger trees, and crushed under foot; or they may be prevented from re-ascending by putting a belt of any sticky compound round the stems of the trees.