Family Tenthredinidae 
Sawflies 
The family Tenthredinidae is represented by more than 730 species in the United 
States and Canada. The larvae are all leaf feeders, leafminers, gall formers, or fruit 
borers. Many species are important pests of forest and shade trees and forest 
plantations. 
The antennae of the adults most commonly have nine segments in the Eastern 
United States and range in shape from setaceous and filiform to clavate. The 
mesothorax is without sterno-pleural sutures, the anterior of the scutellum is V- 
shaped, and the posterior margin usually has a distinct posttergite. The tibiae are 
without preapical spurs, and the apical spurs of the front tibiae usually have the 
longer spur cleft at the apex. The larvae range in length from 10 to 37 mm and are 
usually largest in diameter at the thorax. The body is greenish or variously colored, 
sometimes with distinct markings, and is either smooth, glabrous, setiferous, 
tuberculate, or spinous (/04/, 1369). 
Heterarthrus nemoratus (Fallén), the birch leafmining sawfly, an introduced 
species first recorded from Nova Scotia during 1908, is now widely distributed in 
the Northeastern United States and southeastern Canada (/097). Its hosts are 
various species of birch, with gray, paper, yellow, and European white being 
preferred. The full-grown larva is somewhat flattened and whitish, with the head 
and joints of the thoracic legs brownish, and is about 10 mm long. 
In Maine, winter is spent in the prepupal stage and pupation occurs in late spring. 
Female adults (no males have been found) appear during June and early July and 
deposit their eggs singly in slits cut in the edges of mature leaves, apparently at all 
levels in the tree. The larvae feed in the tissues between the upper and lower 
surfaces of the leaf, producing large blisterlike or blotch mines free of frass (fig. 
189). Each full-grown larva constructs a cocoon within its mine. The leaf then falls 
F-519525 
Figure 189.—Mines and cocoons of 
Heterarthrus nemoratus, the birch 
leafmining sawfly, in leaf of paper birch. 
398 
