904 ^A^ INTRODUCTION TO ENTOMOLOGY 



become full-grown the infested bush is completely stripped of its 

 foliage. The larvas are at first whitish, as they increase in size the 

 color changes to green ; after the first molt the body becomes covered 

 with many black spots and the head is black; at "the last molt they 

 lose their black spots and assimie a uniform green color tinged with 

 yellow at the ends. When full-grown the larvs descend to the 

 ground and spin their cocoons, either just below the surface of the 

 ground or beneath rubbish; sometimes the cocoons are attached to 

 the stems or leaves some distance from the ground. A second genera- 

 tion of the sawflies appears late in June or early in July; and some- 

 times a third generation is developed; this makes it necessary to fight 

 this pest throughout the spring and summer. The larvae can be easily 

 destroyed in the spring by spraying the bushes with Paris green or 

 with arsenate of lead; later when the fruit is near maturity fresh 

 hellebore should be used at the rate of four ounces in two or three 

 gallons of water, or as a dry application, one pound in five pounds of 

 flour or air-slacked lime. 



The pear-slug, Calnoa cerasi. — This is a well-known pest of pear, 

 cherry, and plum. It causes the leaves of the infested tree to turn 

 brown. When such leaves are examined it is found that the injury 

 is due to small, slimy, slug-like larvs, which have eaten off the upper 

 surface of the leaves, leaving the skeleton of veins and the lower 

 epidermis to turn brown, wither and fall; sometimes trees are entirely 

 defoliated in this way by midsummer. When full-grown the larvce 

 descend and burrow into the ground a short distance, where each 

 constructs an earthen cell in which it transforms. A second genera- 

 tion of the sawflies appear and lay their eggs about three weeks later. 

 The larvce can be destroyed by the use of arsenate of lead spray or 

 by dusting the leaves with freshly slaked lime. 



The rose-slug, Clddius isonienis. — Often in the summer our rose- 

 gardens look as if fire had swept over them, so scorched and brown 

 are the leaves. The cause of this apparent conflagration is a trans- 

 parent jelly-like slug, greenish above and yellowish below, which eats 

 the upper surface of the leaves, leaving patches of the lower surface 

 and the veins. These slugs usually feed by night and remain hidden 

 on the lower surface of the leaves by day. When ready to pupate they 

 crawl down or drop to the ground and burrow beneath the surface ; 

 here each makes a little cell and then transforms. The adult fly is 

 shining black with smoky wings and with the fore and middle legs 

 grayish or dirty-white. The female is 5 to 6 mm. in length. There 

 are two broods a year, one in June and one in August. The last 

 brood passes the winter in the ground.. This pest can be destroyed 

 with a solution of whale-oil soap, or with kerosene emulsion. 



Family ARGID^ 



The Argid Saw-flies 



This family has been recently separated from the Tenthredinidas, 



from which it is distinguished by the absence of a post-tergite. This 



is a distinct apical plate borne by the scutellum, which is present in 



all of the Tenthredinidffi and absent in this family. 



