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contend with two classes of pests which injure their crop. The 

 first of these are noxious insects ; the second, parasitic fungi. 



Insects vary greatly in their shape, size, and colour, but on 

 broad lines they all possess, when seen in their full-grown, stage, 

 certain features which differentiate them from other animals. They 

 possess three pairs of legs, attached to a body divided into three 

 definite portions a head, a thorax, and an abdomen. 



Some of them indeed, the majority undergo during their 

 development well-marked transformation or stages : 1st, the egg ; 

 2nd, the larva or caterpillar ; 3rd, the pupa or chrysalis ; 4th, the 

 adult or imago stage. Moths and butterflies, amongst others, 

 belong to this class. In two or, may be, three periods of their 

 transformation they take no food, and are fixtures ; during these 

 periods they do no actual harm. Thus, butterflies and moths are 

 inert in the egg as well as the pupa stages ; and some of them, such 

 as the codlin moth for instance, do not feed. Yet it is during 

 these periods of rest and transformation that it is often easier to 

 attack them. These insects undergo what is called complete trans- 

 formation, in contradistinction of others which undergo incomplete 

 transformation. This second class, such as grasshoppers and 

 locusts, have eggs which, in hatching, give forth young insects which 

 only differ from the full-grown ones in size and in possessing no 

 wings. Instead of changing from larva to pupa, they proceed, by 

 a series of moulting or casting off their skin, to the mature stage, 

 and become imago. During these successive moultings they are 

 known as " nymphs." 



Again, some insects lay eggs, and are "oviparous"; while others 

 bring forth their young alive, and are "viviparous." The majority 

 of them, however, proceed from the egg, whether that egg is 

 deposited and cemented to the plant by means of a viscous secretion 

 or whether they give birth to young ones. In the latter case the 

 female insect generally carries the egg internally until the hatching 

 period arrives. 



So much for the life history of insects, considered broadly. A 

 number of varieties depart from the pattern laid down in several 

 minor details which cannot be touched upon in this paper, although 

 a clear understanding of these particularities is of great assistance 

 in combating pests. They often constitute the weak point of the 

 armour it is meant to penetrate, and serve as a guide in directing 

 the attack against them. 



Almost as important as an undertaking of the life history of 

 pests is a knowledge of the manner they attack plants when taking 

 their food. 



In that respect noxious pests may be considered, irrespective of 

 their classification, names, shape, or colour, into two general types : 

 biting or chewing insects and sap-sucking insects. The former are 

 often leaf-eaters or bark-nibblers, or, again, wood and fruit borers. 

 They are provided with jaws by which they can gnaw the surface 

 of the food-plant, and chew it. 



