NOTES ON THE POPLAR SAW-FLY 



151 



NOTES ON THE POPLAR SAW-FLY {TRICHIO- 

 C AM PUS VIMINALIS, FALL).i 



By Ronald C. Fisher, B.Sc. 



On examination of the young Poplars in a nursery at the 

 Royal Botanic Gardens, Kew, on 2nd August 192 1, peculiar 

 swellings were observed on the petioles of many of the 

 leaves. Closer examination was made and a number of 

 saw-fly caterpillars were found feeding on the underside and 

 at the same time a small larva was seen to emerge from one 

 of the swellings. Larva; and leaves were collected for the 



Fig. I. — Leaf Petiole and Egg-slits. (Enlarged.) 



laboratory experiments on which the following notes are 

 based. 



Two species were found to be present and were identified 

 from Cameron's ^ description as Trichiocampus viininalis, 

 Fall, and Croesus septentrionalis, Leach — the latter in small 

 numbers. Large numbers of infected petioles were examined 

 for the presence of eggs, as it was evident that the peculiar 

 swellings were egg-slits made by the adult saw-fly and in 

 each of which an Q.gg had been deposited. Unfortunately, 

 the search was somewhat unsuccessful, only one Qgg being 

 found ; all the others had already hatched. It was thus 

 apparent that the observations made were commenced at 



^ This species is said to be widely distributed throughout Britain. 

 2 Monograph of the British Phytophagous Byme?2optera, vol. ii., Ray 

 Society, 1884. 



