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Saw-flies — Part 2

The young larva on hatching makes a semi-circular cut through the upper surface and crawls on the top of the leaf. At first it is nearly white in color, with a yellowish brown head. Almost immediately a slimy, olive-colored liquid begins to exude over the whole body; the head appears black under the slime, and the body becomes dark. The anterior segments of the thorax swell out and the head is retracted, so that the little larva appears club-shaped. It begins feeding on the upper surface of the leaf, eating out small holes the size of a pinhead. This work continues and increases as the larva grows until the leaf becomes entirely skeletonized. Full size is reached in less than a month. The larva casts its skin four times, and usually eats its cast skin for its first meal after each molt. When full grown it molts a fifth time, leaving its cast skin as a slender line of slime attached to the leaf. It now appears as a light orange-yellow worm, perfectly clean and dry, with no slime. It then crawls down the plant to the ground, penetrating for half an inch or more and forming a little cell the sides of which it moistens with saliva, thus forming a kind of cocoon of firm texture, more or less impervious to water.

Near Washington the first generation of larvae leaves the trees by the end of June, and a second generation begins to appear soon after; but in New York State many of the individuals of the first generation pass the winter in their cocoons. The insect hibernates below the surface of the ground, and the flies appear the following April or May.

No insect is easier to destroy than the pear slug. All of the insecticide mixtures kill it readily, and even throwing dust over the leaves will destroy it.