510 



APPENDIX II. 



THE PREVENTION' AND DESTBUCTION OP INSECT PESTS. 



To be able to cope with the numerous insect attacks which our 

 fruit, vegetable, and other crops and stock suiFer from, it is essen- 

 tial that we know certain entomological facts, and something of 

 the life-histories and habits of those insects we wish to destroy. 

 A knowledge of some of the simplest elements of entomology will 

 enable us to understand the why and the wherefore of applying 

 certain remedies in certain ways and at particular times. {Vide 

 chapter vii.) 



Vertriin insects are injurious in one stage only, others in two stages, 

 and those witli an incomplete life-history during their irhole life-cycle, 

 from the hatching of the egg onwards. — In the majority of groups 

 it is the larva that does most harm, as in the wireworms or larvas 

 of the click beetles {Elaters), the leather-jackets or larvif of the 

 daddy-long-legs {Tipididir), the surface-larvte or caterpillars of the 

 dart-moths [Noctiue), and the root-eating maggots, the larvic of true 

 flies {IHptera). There are, nevertheless, many exceptions to this 

 general rule : for instance, both larva and adult of the cockchafers 

 {Melolonthidm) do damage ; the larva as well as the imago of the 

 flea-beetles {Halticidce), the pea weevils {Sitones), the raspberry 

 weevil {Otiorhynchus), and asparagus beetle (Crioceris) also cause 

 considerable loss in our fields and gardens. In the case of flea- 

 beetles and others the adults do most harm, the damage caused by 

 the larva; being of secondary importance. Those insects, such as 

 plant-lice, which have an incomplete metamorphosis are destructive 

 in all their stages. With the exception of this last group, the lai-ra, 

 pupa, and adult have generally different habitats. In some insects we 

 can best get at the larva to destroy it, in very few the pupa, whilst 

 many we can attack whilst in the adult phase. The egg masses 



