502 Gall-Gnats on Osiers and Willows, [nov., 



When the other leaves fall in autumn, those of the gall 

 remain — brown and withered looking. Pupation takes place 

 in the gall. 



Cecidomyia (Dasyneurd) terminalis. 

 This brown-black fly is the cause of the swollen galls at the 

 apices of the shoots of 5. fragilis, and 5. alba. 



As many as twenty to thirty larvae may be found in the gall. 



Fig. 5. — Galls of Cecidomyia heterobia on Salix triandra (two-thirds natural size) 



Cecidomyia (Rhabdophaga) heterobia. 



This gall-gnat is the cause of the rosette galls at the apices of 

 the shoots of 5. triandra, and 5. cinerea, and of the galls on the 

 male catkins of »S. amygdalina. The infested catkins are 

 deformed, while the presence of the orange-coloured larvae at 

 the apices of the shoots prevents shoot development. 



The gall-gnat is dusky-brown to black in colour, with the 

 under surface of the abdomen yellow. The damage can be great. 



Last year I had both from England and from Ireland examples 

 of the damage of this insect sent to me. One observer wrote 

 me from Ireland : " Our best brown-skin osiers are attacked, 

 the best osiers for wicker-work ; the green-skinned varieties are 

 not attacked, but even isolated shoots of the brown growing 

 among the green are attacked." The whole crop in this case 

 had to be cut down. The trade names of the attacked osiers 

 were Norfolks (chiefly), Black Mauls or Mules, and Spaniards — 

 these all being varieties of S. triandra. I bred out from the 

 galls during the summer many flies and also some parasites of 

 the gall-gnats. Pupation takes place in the gall. 



The remedial measure is to cut away the galls and burn the 

 enclosed brood. 



