486 



APPENDIX II. 



THE PREVEN"TION AN"D DESTRUCTION OP INSECT PESTS. 



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

 fruit, vegetable, and other crops and stock suffer from, it is essential 

 that wo 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.) 



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

 and those with an incomplete life-history during their whole 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 larvae of 

 the click beetles {Slaters), the leather-jackets or larvte of the daddy- 

 long-legs (Tipulid(e), the surface-larvEB or caterpillars of the dart- 

 moths (Xoctuce), and the root-eating maggots, the lar^'se of true flies 

 [Diptera). There are, nevertheless, many exceptions to this general 

 rule : for instance, both larva and adult of the cockchafers {Melolon- 

 thida') do damage ; the larva as well as the imago of the flea- 

 beetles {Halticiche), the pea weevils (Sitones), the raspberry weevil 

 (Otiorhynchus), and asparagus beetle {Crioceris) also cause con- 

 siderable 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, wliich have an incomplete metamorphosis are destructive in all 

 their stages. AVith the exception of this last group, the larva, 

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

 get at the larva to destroy it, in others the pupa, whilst a few we 

 can attack whilst in the adult phase. Numbers can be got rid of in 



