June, I9I2.] Webster: AIoults of the Pear-Slug. 125 



Body of c? about 31 mm. in length; antennae spotted. The outer extrem- 

 ities of the subgenital plate bent upward and inward and produced into 



sharp points herbardi sp. nov. 



Vertex of the head rounded, no thorn. 



Body of J' about 25 mm. in length ; antenna spotted relini sp. nov. 



THE NUMBER OF MOULTS OF THE PEAR-SLUG, 

 CALIROA CERASI LINNE. 



By R. L. Webster, 

 Ames, Iowa. 



In the course of some experiments with the pear-slug, Caliroa 

 ccrasi Linne, in the insectary of the Iowa Agricultural Experiment 

 Station at Ames, considerable interesting data on the moults was 

 obtained. A brief account of this work in general has already been 

 given by the writer (1911). It seems well, however, to give the whole 

 in detail here, as a study of the moults and head widths of this par- 

 ticular insect. The notes were made during the summers of 1909 and 

 1910; in 1909 by the writer, in 1910 by Mr. T. M. McCall and the 

 writer. 



A short account of the life history of this insect follows. 



The larva is a dark, almost black, slimy slug, about % of an inch 

 long when full grown, which feeds on cherry, pear and plum leaves. 

 These slugs feed on the upper side of the leaves, eating out all the tis- 

 sue except the veins and the lower surface. The injured leaves be- 

 come dry and brown and fall from the trees, which are sometimes left 

 entirely bare of foliage in midsummer. The slugs appear twice dur- 

 ing the year in central Iowa, the first brood coming on about the 

 middle of June, the second about the third week in July. The insect 

 winters in the larval stage in the ground. 



Harris (1841) said that the larvae moulted five times, Dyar (1895) 

 said that there were six stages (five moults to maturity), and also 

 gave some measurements of the head widths. Marlatt (1897) in his 

 account of the insect said that there were five moults. So there has 

 been no difference of opinion regarding this essential point. How- 

 ever, the measurements which follow will show that considerable 



