274 INSECTS AFFECTING VEGETATION 



males, however, are quite lively, flying from one rose bush to another 

 and hovering around their less active partners. 



The female in depositing her eggs turns a little to one side, un- 

 sheaths her delicate saw-like ovipositor, and thrusts it between the 

 two cuticles of a leaf, depositing a single egg in each incision. The 

 egg is of circular outline, much flattened, and measures about one- 

 twentieth of an inch in diameter. Hatching begins in from ten days 

 to two weeks after the eggs are deposited. The larvaa or slugs are to 

 be found at work as early as the 1st of May in the District of Colum- 

 bia, but their appearance in numbers is seldom noticed until the 

 second or third week of that month. Feeding takes place chiefly at 

 night, and always on the upper surface of the leaves, the lower sur- 

 face, ribs, and midribs remaining as a skeleton. The leaves are prac- 

 tically always skeletonized, not eaten into as in the case of the other 

 two rose slugs, except when the larvae are nearly grown. During the 

 daytime the larva usually rests concealed on the under surface of a 

 leaf. 



Sometimes the larvae are so abundant that not a leaf on a bush is 

 spared, and the foliage looks as though it had been scorched by fire, 

 and eventually drops off. The larvae are stated to be between two 

 and three weeks in attaining their growth. They cast their skins 

 several times, leaving them fastened to the leaves. After the last 

 molting they lose their greenish hue and become opaque yellowish. 

 They then descend into the earth to a depth of an inch or more, and 

 each constructs for final transformation a somewhat fragile oval cell 

 or cocoon coated with particles of earth. Here the insect remains as 

 larva until the following spring, when it transforms to pupa shortly 

 before issuance in May. The species is single-brooded, in which 

 respect it resembles many other species of sawflies. 



This rose slug and the others which will be discussed are quite 

 easily controlled by several different methods. A strong stream of 

 water directed upon the plants from different sides by an ordinary 

 garden hose or large syringe, if applied every day or two, will soon 

 rid rosebushes of the pest. This is at the same time an excellent rem- 

 edy for rose aphides or plant-lice. The insects are dislodged, fall to 

 the ground, and are unable to reinfest the bushes. 



Where it is possible to apply them without danger of poisoning 

 human beings or disfiguring the plants for ornament, different poi- 

 sonous preparations are useful. Of these, Paris green, either dry or 

 in solution, arsenate of lead, and white hellebore are good remedies. 

 Paris green is best used as a spray in the proportion of an ounce to a 

 gallon of water. Applied dry, it is mixed with 20 parts of flour or 

 similar diluent and puffed on the plants by means of a powder 

 bellows. For use in large gardens, however, the poison is employed 

 at the rate of 1 pound to from 75 to 125 gallons of water, lime being 

 added in about the same proportion as Paris green to prevent scorch- 

 ing. For properly mixing and applying this insecticide a sprayer of 

 good quality should be used. Sprinkling with a watering pot or with 

 a whisk broom will not answer the purpose and is, moreover, danger- 

 ous to tender foliage. The Paris green is first mixed with a small 



