34-2 PROTECTION AGAINST INSECTS. 



Caterpillar 10 mm. long, with 10 prolegs, dark green, darker 

 on the back, with two brighter green stripes along the sides ; 

 head and prothoracic shield shining black. 



ft. Life-history. 



The moth appears in August and the beginning of September. 



The eggs are laid at the base of young larch shoots, and 

 remain over winter. The caterpillars appear in May or June, 

 and pupate at the end of July or in August in a silken cocoon 

 amongst the needles, on twigs or, when the insect is very 

 numerous, in bark cracks. Generation annual. 



c. Relations to the Forest. 



The caterpillars usually attack only old larch, and chiefly 

 sickly trees, but when very numerous 

 they also attack healthy trees, and 

 underwood of spruce or P. Canbra 

 growing below the larch. They eat 

 the needles, at first those of the 

 lower shoots, subsequently climbing 

 . T I to the summit of the trees. The 



insect sometimes appears in such 



Fig. i76.-2br<r pini- numbers to completely strip the 



cofana, Zll. trees of needles, and entire woods 



may then appear with a brown 



canopy, as if the needles had been burned. As a rule 

 fresh needles appear during an attack, but if it should last for 

 2 to 8 years, even the healthiest trees will succumb. Badly 

 stocked woods on shallow soil and with a southerly aspect 

 suffer most of all. 



This insect is common in Switzerland, and has been 

 observed over fairly large tracts of forest in 1855-56-57, 

 1864-65, 1878-79 in the Ober Engadin, Wallisand Graubundt. 

 In 1879 in the Ober Engadin, where larch is the dominant 

 species, over 15,000 acres of forest were attacked by it. Also 

 in 1889, in the Tyrol. It is not uncommon among larches in 

 Britain. 



