1885.] ^g^ 



THE LARVA OF F^BISCA OPFRESSANA AND ITS HABITS. 

 BY JOHN n. WOOD, M.B. 



In the course of his valuable " Notes on British Tortrices," Mr. 

 Barrett has given us (Yol. xx, p. 267) descriptive accounts of the 

 larvae of all our Pcediscce with the exception of three. With one of 

 these three, P. oppressana, I had the good fortune to become acquainted 

 four seasons ago, and in each succeeding year I have been able to 

 renew acquaintance with it. Most of our books are silent on the early 

 stages of the insect, but Dr. Knaggs in his " Gruide " says, in the bark 

 of poplar and Merrin's Calendar gives September as the time of 

 feeding — conclusions formed I suspect on the circumstance that the 

 perfect insect appears early in the summer, and has an evident affection 

 for the trunks of poplar. But if the Entomologist wants to find it, 

 let him search the terminal buds on the short side-spurs of the black 

 poplar {Populus nigra) in March and April — if he see a small brown 

 Bomewhat curved projection standing out from the bud, which on closer 

 inspection turns out to be a hollow tube of " f rass " communicating 

 with the interior, he may know that he has found oppresmna. The 

 only insect I am acquainted with that could be mistaken for it would 

 be Hedya aceriana, but the latter feeds later in the year, and the frass- 

 tube instead of projecting at right angles from the bud lies flat upon 

 ; it. I have hitherto failed to learn where the egg is deposited or when 

 it hatches. I have confined the perfect insect without getting eggs, 

 and have carefully examined the buds early in the year without dis- 

 covering traces of larvae, where afterwards at the end of March I have 

 found them present. At that time the larvae, little purplish-brown 

 creatures with rather conspicuous hairs, were rather more than one line 

 long and were actively engaged feeding in the bud. And were I to 

 venture an opinion it would be that the larva lives through the winter 

 closely hidden within a bud, into which it penetrates by an opening 

 too small to be detected, and when the approach of spring awakens it 

 to renewed activity, it then for the first time constructs the character- 

 istic frass-tube, to serve as a general refuse-pipe and ventilator. The 

 bud occupied in March gets eaten out and killed, and then some time 

 in April the larva passes to another, within which it remains until it 

 leaves it to spin up among rubbish in the first or second week in May. 

 The last bud attacked has its growth and development retarded but is 

 not killed, for the tree has begun to shoot and can resist the injury. 



The larva is semi-transparent, somewhat shining, short, fat, and 

 soft-looking, and of a pale brown colour. Head very small, deep 

 black. Thoracic plate and prolegs also deep black. A small black 

 plate on anal segment. 



Tamil gton, Ledbury : 



November, 1885. 



