114 PROTECTION OF WOODLANDS. 



favourable breeding-place for bark-beetles (Bostrichus linealus, 

 &c.), whilst in the stumps of trees that have had to be felled in 

 consequence of the injuries sustained by the destruction of the 

 needles, the weevils or rostral-beetles (Curculionidse) also deposit 

 their ova for the rearing of their brood. 



But fortunately there are also influences unfavourable to the 

 numerical increase of insect enemies, as well as favourable con- 

 ditions. Among the causes hindering their too prolific repro- 

 duction when once the attacks of any insect have attained 

 calamitous proportions, and even in some cases bringing them to a 

 natural close, may be mentioned the following : 



Ungenial weather, violent downpours of rain, and damp, cold, raw 

 days, especially during the time of swarming, or at the time cater* 

 pillars are changing their skin, when many succumb to the cold* 

 But on the other hand, species that hibernate as caterpillars or 

 chrysalides are very little sensitive to wintry cold ; they get frozen 

 and then thaw again without suffering any apparent injury. 



Diseases and epidemics, which often kill off the caterpillars in a 

 short time, and fungoid attacks, to which caterpillars and pupae 

 hibernating under moss are especially liable, often reduce large 

 numbers quickly. 



Natural enemies of the insects, finally, often appear in unusual 

 numbers, and assist in the war that is being waged against these. 

 The chief of these enemies are : 



1. Among Mammalia. 



Bats (species of Vesperugo), which are especially inimical 

 cockchafers and moths. 



Moles (Talpa europ&a) destroy grubs and mole-crickets (< 

 lotalpa vulgaris) ; shrew (Sorex vidgaris), hedgehog (Urinaceus 

 europteus), squirrels (species of Sciurus), weasel (Putorius mdgaris), 

 pole-cat (P. f&tidus), stoat (P. ermineus), badger (Meles taxus^ 

 and fox ( Vulpes vulgaris), devour a large number of beetles and 

 chrysalides, as has often been proved from investigations made of 

 the contents of their stomachs, and from examination of their 

 excreta. 



Wild-boar and tame pigs are very fond of grubs, hairless cater- 

 pillars, and chrysalides, and love to hunt for them in the 

 or under the moss. 



