260 FOREST ENTOMOLOGY. 



therefore, that this must have a very appreciable effect on the 

 increment. 



The imago stage is, as a rule, of short duration. Many examples 

 may be found on the wing from March to November, but the majority 

 of arboreal species are most abundant from May to July. 



The general characters of the imago may be given as head tufted 

 with hairy scales, often partially hiding the eyes ; the compound eyes 

 usually large and spherical ; antennas invariably simple, and never so 

 long as the anterior wings ; thorax usually short ; abdomen moder- 

 ately stout in both sexes, more especially in female, and often 

 terminated by a tuft of bristles in the male. 



The larva is from ^ to f inch in length, usually with sixteen feet, 

 head and shield horny, and the anal segment generally has a horny plate 

 on the dorsal surface. The duration of life and habits vary according 

 to the food of the species. Thus, for instance, those living on the 

 foliage of deciduous trees must be fully developed prior to the fall of 

 the leaf, or even before the leaves become too hard, while those feed- 

 ing under bark can live comfortably throughout the winter months. 



The pupa is either enclosed in a cocoon or web spun by the larva. 

 The abdominal segment is often armed with minute spines. The 

 pupal stage, like that of the larva, is also very variable. 



Tortrix viridana, Linn. (Green Tortrix Moth). 



There is perhaps no species of insect whose injuries are more 

 conspicuous than those of the green Tortrix, or oak-leaf roller moth. 

 Often as early as the end of May, or beginning of June, the larvae 

 are so abundant as to almost completely defoliate the trees. As this 

 occurs just at the time when the tree is actively growing, it is obvious 

 that in consequence of defoliation the loss of increment is enormous. 

 By way of revenge, as it were, the tree subsequently produces a crop 

 of late green shoots Lammas shoots, as they are termed, and 

 though to some extent amendment may be made, yet it is just 

 possible that there may be such a physical difference between the 

 spring and autumn formed cells as to cause technical depreciation 

 of the timber. 



It is generally asserted that this species confines itself entirely to 

 the oak. Such, however, is not always the case, as I have often bred 

 it in comparatively small numbers from hazel and ash. It has been 



