222 HYMENOPTERA. 



5, the same, natural size ; 8, an antenna enlarged ; 4, the 

 larva while feeding ; 6, the same, at rest ; 7, the cocoon ; 9, an 

 egg enlarged. 



Of the genus Dolerus, known by the second submarginal cell 

 receiving two recurrents, D. arvensis Say, is a common blue- 

 black species found in April and May on willows. 



The genus Selandria is the most injurious genus of the 

 family. It embraces the Pear and Rose-slugs, the Vine-slug 

 and the Raspberry slug. The flies are small, 

 black, with short and stout nine-jointed an- 

 tennae, and broad thin wings. "The larvae 

 are twenty and twentj^-two-footed, present- 

 ing great differences in appearance and habit, 

 being slimy, hairy or woolly, feeding in 

 companies or alone, eating the whole leaf as 

 they go, or, removing only the cuticle of the 

 leaf, and forming sometimes one and some- 

 times two broods in a year. Selandria vitis, 

 the Vine-slug, is twenty-footed ; it has a 

 smooth skin, and the body is somewhat thick- 

 ened in the middle but slender towards the 

 tail. "While growing, the color is green 

 above, with black dots across each ring, and 

 yellow beneath, with head and tail black. 

 They live upon the vine and are very destruc- 

 tive, feeding early in August in companies, on 

 rig. 148. ^ ne i ower side of the leaf, and eating it all as 

 they go from the edge inwards. There are two broods in a 

 season. The fly is shining black, with red shoulders, and 

 the front wings are clouded." (Norton.) 



S. rubi Harris feeds on the raspberry, appearing in May. 

 The larva is green, not slinry, and feeds in the night, or early 

 in the morning. S. tilice feeds on the linden. The Pear-slug, S. 

 cerasi Peck (Fig. 148, larvae feeding on a leaf of the pear, and 

 showing the surface eaten off in patches ; a, enlarged ; 6, fly), 

 is twenty-footed ; it narrows rapidly behind the swollen thorax, 

 and is covered with a sticky olive-colored slime. It feeds on 

 the upper side of the leaves of both the wild and cultivated 

 cherry and pear trees, and has been found on the plum and 



