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of which will be better understood if one has a good knowledge of the habits 

 and methods of development of the various insects or fungoid pests. Nearly 

 all these organisms are weaker or easier to destroy at some particular period of 

 their existence than at any other. We sometimes hear of Nature preserving 

 her own balance when not interfered with by man, by certain injurious insects 

 being destroyed by others not injurious to plants. Doubtless this does occur 

 to a certain extent, but the real difficulty lies in recognising and preserving the 

 insect friends, and furthermore in being able to secure and rely upon them in 

 sufficient numbers at the right moment to cope with the hordes of rapidly 

 multiplying enemies. 



How Insects Feed. — Insects take their food in two ways : some bite and 

 others suck ; those which bite take, piece by piece, the tissues of leaf, stem, or 

 fruit of their host plant. Because of this they may be destroyed by placing 

 particles of poison upon the surface of the leaves, i.e. by spraying. A large 

 proportion of the injurious insects feed in this way, but there is also an im- 

 portant class which have a proboscis that they push into the cells of the plant 

 and suck out the sap juices. Insects of this kind cannot be destroyed by 

 coating their food plant with particles of poison, for such particles will not 

 enter their alimentary system, consequently one must use against them an 

 insecticide that kills by contact. 



Insecticides. — There are several such insecticides in common use, the most 

 important and safe being caustic alkali insect powder or paraffin emulsion. 

 Insecticides used in spraying may be broadly divided into two classes, viz. : 

 First, internal poisons, or those which take effect by being eaten with the 

 ordinary food of the insect ; and second, external irritants, or those which act 

 from the outside either by closing the breathing pores or causing death by 

 intense irritation of the skin. Substances used to destroy insects are called 

 insecticides ; those used to destroy fungi, fungicides. The most important 

 matter connected with these insect pests and spraying is to attack them on the 

 first signs of their presence, or, better still, to act on the old adage, "prevention 

 is better than cure," for once they are allowed to get the upper hand they are 

 very difficult to dislodge, especially those which roll themselves in the leaves, 

 where the insecticide cannot penetrate. The same remark applies to all the 

 aphides, which breed with such startling rapidity. We have found that an 

 insecticide, even when strong enough to kill every insect, at the same time is 

 harmless to the eggs, enclosed in their shining, hard, shell cases. Hence we 

 have to repeat the sprayings at daily intervals so as to endeavour to wet every 

 tiny insect as soon as it emerges from the egg, and thus prevent their reaching 

 the adult stage for further egg laying. A fruit and hop grower in Worcester- 

 shire has recently imported a large quantity of Californian ladybirds, as an 

 experiment to see whether they will devour aphides in the same good way as 

 they do in their native country. We shall watch this interesting and enter- 

 prising experiment with much interest. The worst feature is that spraying 

 has an injurious effect upon the ladybirds as well as the aphides. 



The Board of Agriculture supplies gratis special pamphlets upon the most 

 common and injurious insect pests, and they contain much valuable informa- 



