186 PROTECTION OF WOODLANDS. 



as are badly grown and somewhat sickly from being suppressed 

 or dominated, and thus cut off from normal supplies of light and 

 air requisite for the due satisfaction of their requirements for 

 healthy development. So long as they are still small, the cater- 

 pillars generally feed in twos on each spine, and leave the midrib 

 standing ; but when they are stronger and nearer the attainment of 

 their full growth, they devour the whole needle, just leaving a 

 little bit of stump, whilst the young spines remain untouched. 



During the month of July they enter into the pupal state of 

 rest, the cocoons being formed between the scales of the bark and 

 on the branches of the foliage. In about 2 or 3 weeks the fully- 

 developed saw-fly makes its appearance and swarms, when repro- 

 duction is accomplished, and the second ovi-deposition takes 

 place. 



The caterpillars of this second generation come out of the shell 

 during August, and often continue feeding until well into autumn, 

 when they descend from the stems, form their cocoons under the 

 moss covering the soil, and hibernate within these as larvae, for 

 the metamorphosis into chrysalides only takes place during the 

 following spring. 



The above-sketched normal development is not always carried 

 out in full regularity or entirety, for it sometimes happens that 

 single broods, or even whole generations, remain for a whole year, 

 or even for two years, in the cocoon before at length developing 

 into the imago or perfect insect. 



The Pine Saw-fly, which sometimes occurs in very large num- 

 bers, decidedly belongs to the more injurious class of forest 

 insects. Although, as above remarked, it in the first instance 

 attacks crops of sickly growth and backward development, yet, 

 when increasing rapidly in numbers, it also extends its ravages to 

 healthy crops of normal growth ; by interfering then with their 

 development, it very soon brings them into an unhealthy con- 

 dition, and thus directly paves the way for other noxious insects 

 finding in them only too favourable a breeding-place. The 

 immediate damage which the saw-flies themselves commit is 

 checked or minimised, owing to the fact that the shoots of the 

 last year usually remain intact, so that the formation of buds for 

 the next year is not rendered impossible. 



Numerous animals render valuable assistance towards the 

 annihilation of the Pine Saw-fly, above all, the insectivorous 



