CHAP, xiv.] Insect Enemies 317 



a previous and a succeeding year of minor damage may be 

 added (without, however, counting the subsequent ravages of 

 the Scolytidae and Curculionidae, that have also to be reckoned 

 with owing to the sickly state in which the still existing crops 

 are left), and (2) that then parasitic insects (Ichneumonidae), 

 fungoid diseases, and insectivorous birds also increase nume- 

 rically to such an extent as to decimate and finally exterminate 

 the plague in a very short time. Under ordinary circum- 

 stances, however, and especially in mixed woods (as compared 

 with pure or mixed crops of coniferous species only) with their 

 larger numbers of insectivorous song-birds, the tendency to 

 excessive reproduction and increase of noxious insects is held 

 in check by the presence of their natural enemies. So far, there- 

 fore, as may be compatible with other and sometimes more 

 important considerations, all these natural enemies of injurious 

 insects should be preserved and their numerical increase 

 encouraged. The chief of these are : 



A. Among Mammals. 



Bats (species of Vcspcrugo\ which consume large numbers of 

 cockchafers and moths; moles (Ta/pa europea) that destroy 

 grubs and mole-crickets (Gryllotalpa vulgaris); Shrew (Sorex 

 vulgaris}) Hedge-hog (Erinaceus europaeus), Squirrels (species of 

 Sa'urus), Weasel (Putorius vulgaris], Pole-cat (P.foetidus\ Stoat 

 (P. ermineus\ Badger (Meles taxus), and Fox ( Vulpes vulgaris], 

 which devour large numbers of beetles and chrysalides, as has 

 often been proved by the examination of their stomachs and 

 excreta. 



B. Among Birds. 



The most generally useful are the Cuckoo (Cuculus canoris) 

 which is the only bird that eagerly devours the hairy cater- 

 pillars of species like the Pine moth (Gastropacha pini) the 

 Starling (Sturnus vulgaris}, Flycatchers (Muscicapa^ Tits or 

 Titmice (Paridac), Tree-creepers (Certhia familiaris\ Swallows 

 (species of Hirundo), and most singing birds ; then Thrushes 



