4 HEMICHEOA ALNI. 



and reaches close to the top of the outer, which is 

 broadly rounded on the top. The cardo is triangular, 

 and one fourth longer than the mentum, which is 

 broadest at the top. 



The saw is strongly built, has broad, long, and 

 sharply projecting teeth and strong cross bars. The 

 support has also cross bars and is likewise strongly 

 built. 



So far as is known the larvae are cylindrical and 

 green or reddish in coloration ; the eggs are laid in the 

 twigs of the food plants. 



The males are unlike the females in coloration ; 

 both the males of the two British species having the 

 body quite black, and the legs reddish. With our 

 species they are very rare, and both are freely par- 

 thenogenetic, the unfertilized eggs yielding either 

 males or females. 



Hemichroa is most nearly related to Dineura and 

 Camponiscus ; from the former it is known by the 

 constricted lanceolate cellule ; from the latter by its 

 possessing two radial cellules. 



The genus is of small extent, there being only three 

 European and two North American species. One of 

 our species (rufa) is found also in North America. 



Synopsis of Species. 



1 (2) Abdomen black, tibiae black. Alni. 



2 (1) Abdomen red, tibiae white. Rufa. 



1. HEMICHROA ALNI. 



Vol. I, PL XIV, fig. 8 ? ; PI. XXI, fig. 8, Saw. Vol. II, 

 PI. VIII, fig. 2, Larva; PI. XXVII, fig. I, Trophi 

 of Larva. 



Tenthredo alni, Lin., Fn., Sv., 1571; S. N. (2), 925,29; Fab., 

 E. S., ii, 115, 39; Fall., Acta, 1808, 

 109, 46; Schaef., Ic., pi. 110, figs. 6, 7 ; 

 Reaum., Mem., v, pi. ii, figs. 1, 2 (lar.) : 

 Lep., Mon., 129, 391. 

 australis, Lep., Mon., 71, 217. 



