280 



FOREST ENTOMOLOGY. 



April, and then, together ivith the larva or pupa in the shoot, cut off 

 and burned. This method is apparently tedious, and when the lead- 

 ing shoot is removed considerable disfigurement ensues, but as a tree 

 the larch has wonderful recuperative powers of taking a lead from a 

 side branch, so that the labour would be well repaid. 



Gracillaria stringella, Fab. 



This species is often very injurious to the foliage of lilac (Syringa 

 vulgaris). The larvae live gregariously within the epidermal skins of 

 the leaves, and cause very conspicuous blotches, as seen in fig. 267. 



Mr Collinge has worked out the life- 

 history of this species, and the following 

 account is given by him: 1 



" The observations and experiments were 

 made on nine trees about five feet in height 

 and growing five or six feet apart. 



" The moths of the first brood were noted 

 on May 24, rather later than in 1904. The 

 eggs were noticed on both the upper and 

 under surfaces of the leaves a few days 

 later, 27th and 28th, and the caterpillars 

 hatched out on June 4. They at once made 

 their way into the leaves, and commenced 

 to feed upon the soft parenchymatous 

 tissue between the upper and lower epi- 

 dermis. The largest number found in any 

 one leaf was thirteen. 

 " Sometimes the whole of one side of the leaf was tunnelled ; in 

 other cases the basal half was blistered before the apical ; whilst in 

 others the blisters were irregular and scattered over the leaf. 



"The young larvae are almost transparent and glossy; a little later 

 they have a faint yellowish tinge, with a narrow median green line, 

 caused by the green chlorophyll in the intestine. After feeding in the 

 leaf for about three weeks, they creep out on to the surface and 

 commence to feed on the epidermis, the leaves rolling up laterally or 

 from the apex. About ten days later they become full fed, and are 

 slightly over a quarter of an inch in length, with a prominent brown 



1 Eeport on the Injurious Insects and other Animals (Midland Counties), 1906. 



Fig. 267. Leaf of lilac (Syringa 

 vulgaris) injured by the min- 

 ing larvce of Gracillaria syrin- 

 gella. 



