312 PROTECTION AGAINST INSECTS. 



up to the top, but in Scots pine, only as far as the rough bark 

 extends. Later the eggs become of a pearly grey colour, and 

 hibernate without any protective covering. 



The caterpillars hatch at the end of April, or the beginning 

 of May. They remain for a few days (2 to 6) in small groups 

 near their hatching place, and then ascend to the crowns of 

 the trees. Until they are half -grown, they are able to let 

 themselves up and down by threads should they be disturbed. 

 They become full grown by the end of June, or the beginning 

 of July. When young, they are rather sensitive to changes of 

 weather, and are easily blown down by the wind, and may then 

 fall on to young forest growth. 



Pupation takes place at the end of June or the beginning of 

 July, and the pupae may be found fixed by a few threads in 

 bark-cracks low down on the stems, also on needles of low 

 branches, and even on undergrowth. 



The moth emerges in 15 to 20 days after pupation, the active 

 c? appearing a few days before the ? . 



Generation annual. The insect appears sometimes in truly 

 formidable numbers. The moths, especially the $ , are very 

 active, and may fly for long distances in swarms, but usually 

 remain localised. 



L. monacha is tolerably common in many localities in 

 Britain, chiefly in the south of England, but is not generally 

 regarded as an abundant insect. It is rare in conifer woods 

 and, consequently, seldom if ever destructive ; its usual food- 

 plant appears to be the oak. Indeed most British lepidopterists 

 seem to be unaware that it is a conifer feeder. 



c. Relations to the Forest. 



This species attacks all conifers, but prefers the Scots pine 

 and spruce, and tall poles and old trees of these species to 

 younger ones ; it also, however, attacks young growth and also 

 broadleaved trees, such as beech, hornbeam, birch, oak, orchard 

 trees, least of all the ash and alder. In cases of scarcity of 

 other food, it will not disdain low shrubs. 



The caterpillars devour the needles and buds. When young 

 they bore into the tender shoots, causing them to wilt ; the 



