HOW TO GROW GOOD FENCES. 253 



defoliated by caterpillars, which progressed from tree 

 to tree in squads of numberless individuals, only seek- 

 ing a new site of action when the former one had 

 been despoiled of every vestige of leaf and bud. 



But it is not only the hawthorn which becomes 

 attacked by insects : all other hedge-row trees and 

 shrubs have their peculiar enemies, to describe which 

 would take more space than we have to spare, and we 

 therefore conclude the chapter with a few remarks 

 upon the weeds of dirty hedge-rows. These harbour 

 various insects, which migrate to our crops, and do an 

 immense amount of injury. For instance, such plants as 

 Jack by the Hedge {Erysimum alliaria), treacle mus- 

 tard {Sisymbrium officinale), wild mustards, and other 

 forms of Cruciferce, in hedge-rows, afford a winter 

 nidus for the turnip flea beetles {Raltica concinna 

 and H. nemorum)* from which they take their flight 

 to the more delicate turnip and swede crops as soon 

 as these come up. 



Birds need only here be mentioned incidentally, as 

 there is still a conflict of opinions as to the use of the 

 bird family to the farmer ; and those species which 

 mostly build in and frequent our hedges are perhaps 

 those upon which evil suspicions are most universally 

 held. Amongst these are the hedge-sparrow, finch, 

 linnet, and others — and that these are mischievous at 

 times, we are not prepared to deny ; but we should 

 be sorry if the curtailment of hedges, for which we 

 are advocates, should result in the destruction of our 

 small birds, as we conclude most of the species to be 

 at times eminently useful. 



* See How to Grow Good Hoots, pp. 43 and ii of the present 

 work. 



