512 I'REVKNTIDN AND DKSTRUCTION OF INSECT PESTS. 



soft-soap answers this purjiose ; other subsfcinces, such as quassia, 

 put in the wash, arc of value, but are not es.^oiitial for killing most 

 aphides. Soft-soap also adheres to the aphides' skin, and is useful 

 besides in fixing corrosives and poisons on the insect and foliage. 

 The more soft-soap u.sed, within certain limits, therefore, the better. 

 Certain .substances, as paraflBn, corrode the skin of aphides. Mites, 

 on the other hand, breathe cutanoously, and not through spiracles ; 

 nicotine or soap washes have less eftert on them. 



i)a the head of an iiiwct u:i' ham ohsfn-vd, besides the mouth, tiro 

 kinds of eyes, ximp/e (ind compound, and in front of the two large 

 compound eyes a pair of jointed hora-Uke processes, the '■^feelers" or 

 antcnnir.— What are these feelers for '! They are sense organs ; 

 whether they serve for one or two or more sensory fimctions we 

 do not know. One sense is certainly developed in them — namely, 

 "smell." The sense of smell may also be -seated in the jointed 

 palpi attached to the twd lower pairs of jaws. Insects have the 

 sense of smell very acutely developed : they are attracted to their 

 food-plant by its odour, both for feeding purposes and for ovi- 

 position. Plant three beds of carrots in your garden some distance 

 apart : sow one thinly, so that you have no necessity to thin them 

 out ; sow the other two in the ordinary way, and thin out one of 

 these, damaging the plants by bruising as you do so, and leave the 

 soil loose around the plants left in the ground : thin out the thii-d 

 bed in the same manner, Imt sprinkle over it, as you go along, sand 

 soaked in paraffin, so that the sand falls down and covers in the 

 spaces around the young carrots. You will find the middle plot 

 infested with " rust," the flies having been attracted by the smell 

 from the bruised carrots ; the dressed plot and plot one will be 

 practically clean, owing to the paraffin destroying the smell of the 

 plant in the one ease, and no smell being released in the other. 

 The use of these deodorants is very important as a preventive of 

 insect ravages, both for dressing the seed and young plants. 



Thus from studying the structure of an insect we see that we can 

 fight them in three different ways — by poisoning, by asphyxiating, 

 and by destroying the natural smell of the plant. The corrosive 

 action of certain substances mvist also be noted. 



The two meaiis of checking insect ravages are by Prerention and 

 Remedies. — By prevention the appearance of any pest is forestalled, 

 by either maldng the surroundings unfit for them to live in, by 

 the winter destruction of the insects, by trapping, or by the use of 

 deodorants upon seeds and seedlings. In regard to the winter de- 



