VEGETABLE GARDENING, OR OLERICULTURE 17 



This treatment is less dangerous, more easily prepared, and not 

 more expensive than the corrosive-sublimate treatment, and of 

 late has largely replaced it. 



Insects and insecticides. It is not possible, in this connection, 

 to enter into the specific differences which distinguish different 

 families and groups of insects from one another. For our purpose, 

 however, it is sufficient to know that those insects which as a rule 

 are most injurious to crops are of two classes : insects which gain 

 their sustenance by biting or devouring the tissue of the plant, 

 and those which gain their sustenance by sucking the juices of the 

 plant. The first class of insects have jaws fitted for biting and for 

 masticating the plant tissue, and their work is followed by defolia- 

 tion or by the destruction of areas of leaf or stem tissue. The 

 mouth parts of sucking insects are not made for biting, so do not 

 admit of the destruction of plant tissue in that way. Such insects 

 have tubelike mouth parts which they insert in the tissue of the 

 plant to suck its juices. It is evident, therefore, that insects of the 

 two classes must be fought from different standpoints and with 

 different insecticides. 



The first class of insects, which gain their nourishment by eating 

 the tissue of the plants, can, of course, be poisoned, and this is 

 usually successfully accomplished by the use of Paris green or arse- 

 nate of lead in suspension in water. Paris green is used at the rate 

 of 5 ounces of the green to 50 gallons of water, while the arsenate 

 of lead is used in somewhat greater strength I to 2 pounds to 

 50 gallons of water. 



Those insects which obtain their nourishment by sucking the 

 juices of plants can be destroyed only by the use of insecticides 

 which come in contact with the body of the insect. For this pur- 

 pose volatile oils or oil and soap mixtures are usually employed. 

 Kerosene emulsion and whale-oil soap are two of the standard 

 remedies for this class of insects. 



Kerosene emulsion . Kerosene emulsion is made as follows : 



Hard soap or whale-oil soap \ r Ib. 



Boiling water, preferably soft water I gal. 



Kerosene 2 gal. 



