PINE MOTH. 297 



Exceptionally they may hibernate in the bark-crevices. The 

 time of reascension depends on the degree of warmth of the 

 season and on the quarter from which the wind is blowing. 



Pupation takes place at the end of June or beginning of 

 July, either on the needles and twigs of the crown of the tree, 

 or in the larger bark crevices. 



The moth emerges in July, about 20 days after pupation. 



Generation annual ; but sometimes irregular when the insect 

 occurs in great numbers. Very common in Germany. 



c. Relations to the Forest. 



This is the most destructive of all insects to Scots pine 

 forests in Central Europe, as it may appear in large swarms 

 throughout the summer for several consecutive years, and is 

 enormously voracious. The caterpillar also attacks the 

 Austrian and mountain pines, and in case of scarcity of food, 

 both the spruce and larch. It prefers 60- to 80-year-old 

 trees, but when abundant it will attack younger trees, and 

 thickets of young growth and plantations. 



The attack is on the needles. When the caterpillars are 

 very young they gnaw the sides only of the needles, but fully- 

 grown caterpillars eat them down to the sheath, usually 

 leaving the latter, and in this manner completely strip the 

 twigs. 



Even the terminal buds may be eaten. The older cater- 

 pillars prefer needles of the previous year. A single caterpillar 

 will eat a needle in 5 minutes, and may destroy in all 1000 

 needles. After complete destruction of the needles and buds 

 the tree must perish, and as a premonitor of death a few 

 clusters of stunted needles, termed rosettes by Ratzeburg, may 

 appear. 



The trees may recover, if for a pole 200 needles, and for an 

 old tree 400 needles, still remain green. An attack com- 

 mencing in April and lasting till June is the worst, as this 

 affects the formation of wood. An attack generally lasts 

 for 3, occasionally for 4 years, and is at its maximum during 

 the 3rd year. Irregularity in the development of the insects, 

 and degeneration of the caterpillars, which are largest in the 



