398 



REPORT OF STATE BOARD OF HORTICULTURE. 



Fig. 3 — Pear slug: a, last 

 moulted larval skin ; b, 

 larva after castinglastskin 

 — somewliat enlarged (orig- 

 inal). 



leaf that it can be readily watched and its gradual- increase 

 absorption from the leaf and the development of the 

 young- larva can be easily studied with a hand lens. 

 The larva emerges on the upper surface of the 

 leaf through a very regular semicircular cut which 

 it makes near the center of the cell. At first it is 

 clear or free from slime and in color nearly white, 

 except the yellowish brown head : but almost im- 

 mediately the slimy or gluey olive-colored liquid 

 begins to exude over its entire body, giving it the 

 appearance of a minute slug, or soft snail, from 

 which it gets its name. Its head is dark brown, 

 appearing black under the slime, and the body also 

 becomes almost equally dark. The anterior seg- 

 ments are much swollen, covering up and conceal- 

 ing the head and thoracic legs. In common with 

 other saw-fly larvae it has a great number of false legs or prolegs on the 

 abdominal segments ; in this species there are fourteen such prolegs, the 

 terminal pair being wanting, and the tapering tip of the body is usually 

 slightly elevated. 



As soon as the larva emerges from the egg it begins feeding on the upper 

 surface of the leaf, eating out small holes or patches about the size of a pin 

 head or smaller, but never eating entirely through the leaf. The larvse 

 feed almost invariably on the upper side of the leaves and the minute eaten 

 spots which they make at the start rapidly increase in size until much of it, 

 but not the entire surface of the leaf, is denuded, leaving merely a network 

 of veins, or a leaf skeleton, held together by a nearly intact lower epider- 

 mis. Leaves thus eaten turn brown, die, and fall to the ground, the tree 

 being frequently defoliated, except for the effort it usually makes to put out 

 a new growth. 



The characteristic features of the larva are its swollen anterior segments 

 and its olive-colored slimy covering, which last is probably a protection 

 furnished by nature against the attacks of parasitic insects. It is very slug- 

 gish in movement, but has an enormous appetite. Its growth is rapid, full 

 size being attained within considerably less than a month, usually about 

 twenty-five days, the time varying a little with the nature of the weather. 

 It does not alter much in appearance during growth, and ultimately reaches 

 a length of nearly half an inch. It sheds its skin four times during its 

 larval life, and usually eats its cast skin for its first meal after each moult. 



When full grown it moults a fifth time, but on 

 this occasion leaves its cast skin as a slender 

 line of slime attached to the leaf. The dark 

 olive-green slimy appearance which has hitherto 

 characterized the larva is lost with this last 

 moult (see Fig. 3, a, which shows last molted 

 skin), and in its stead it appears as a light 

 Fig. 4— Pear slug : a, cocoon ; b, orange-yellow worm, perfectly clean and dry, 

 enrarledToriS)!' ^'^'P'''"*'" with the head light-colored and only the minute 



