56 



APHIS, OR PLANT-LOUSE. 



It may almost be said of this familiar pest that there are as many varieties of plant 

 lice as there are species of plants in the vorld ; nearly every form of vegetable life 



^ 



Fig. 29A. 



Fig. 29B. 



lias its own Aphis to suck its juices and to impair its vitality. It would, therefore, 

 be an endless task to attempt to enumerate all the different kinds of Aphis that are 

 to be met with and fought against ; the same remedies, however, will apply with almost 

 equal efficacy in all cases, allowance being made for the difference of application requisite 

 in treating, for instance, an apple tree and a wheat plant, a hop vine and a window flower. 

 The illustration (Fig. 29A) given herewith represents a highly magnified winged male and 

 wingless female of the plant-louse attacking the apple (Aphis mali, Fabr.) ; the species 

 infesting other plants are very similar, varying chiefly in colour from pale green to 

 deep black. Fig. 29B represents the winged form of the woolly Plant-Louse of the 

 apple, a group of the larvae, and a twig perforated by the insect. 



The ordinary remedies for this pest are (1) watering the infested plants with strong 

 soap-suds, or a decoction of coarse tobacco : (2) dusting with lime or sulphur ; (3) 

 exposing them to the fumes of strong tobacco. The first remedy is applicable to most 

 cases, and the third only to plants in pots, or those sufficiently small to be covered over 

 while undergoing fumigation. 



Many experiments have recently been made both in England and the United States, 

 for the purpose of finding out a cheap and thoroughly effective remedy against this and 

 other insect pests. Coal oil (or kerosene) is so cheap, so universally an article of 

 domestic consumption, and so deadly to all insect life, that experiments have been 

 especially directed towards its employment as an insecticide. The great difficulties to 

 be overcome are its destructiveness to vegetation, when applied undiluted, and the 

 almost impossibility of diluting it, beyond a mere mixing of a momentary character with 

 water or other liquid. These difficulties have, however, been at last solved by means 

 of " emulsions." One of these, recommended by the United States Department of 

 Agriculture, is made as follows : — 



" Take of refined kerosene (coal oil) two parts, and of sour milk one part. Mix in 

 a pail, or tub, by continuous pumping with a force-pump back into the same vessel 

 through the flexible hose and spray nozzle. After passing once or twice through the 

 pump the liquids unite and form a creamy emulsion, in which finely divided particles of 

 oil can be plainly detected. Continue the pumping until the liquid curdles into a white 

 and ^listening butter, perfectly homogeneous in texture, and stable. The time required 

 for producing this butter varies with the temperature. At 60° it will be from one-half 

 to three-quarters of an hour ; at 75°, fifteen minutes; and the process may be still more 

 facilitated by treating the milk up to, but not beyond, the boiling point. 



" Upon standing for a day or two the milk (if sweet has been used) will curdle, but 

 it only requires to be stirred, not churned again, to bring it back to its former smooth- 

 ness. But if sour milk is used no fermentation ensues, and if not exposed to the air the 

 1 mtter can be kept unchanged for any length of time. 



