HYMENOPTERA. 613 



sions half-way round the terminal twigs of the tree. What 

 their object was in doing this is a mystery. 



The Rose-Slug, Monostegia roscB (Mon-os-te'gi-a ro'sae), 

 — 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 transparent 

 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 mid- 

 dle legs grayish or dirty-white. The female is about one 

 fifth inch 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. 



The Pear-tree Slug, Eriocampa cerasi (Er-i-o-cam'pa cer'- 

 a-si). — The eggs of this species are laid on the leaves of pear 

 and cherry trees, at the beginning of the summer. In about 

 ten days the slugs hatch; they are at first whitish, but soon 

 cover themselves with a dirty green, gummy excretion. 

 When full-grown these larvae attain the length of half an 

 inch. The fore part of the body is enlarged; and they rest 

 with their tails in the air, and appear, as Mr. Harris aptly 

 observes, like minute tadpoles. These, like the rose-slugs, 

 eat only the upper surface of the leaves. The species is two- 

 brooded ; the second brood passes the winter in the ground. 

 The larvae can be destroyed in the same way as the preced- 

 ing species. 



The Currant-worm, Nematus ribesii (Nem^a-tus ri-be^si-i). 

 — This well-known enemy of currant and gooseberry bushes 

 belongs to the class of criminal emigrants, and has gained a 

 foothold and flourishes in our midst in spite of us. The fe- 



