36 



Aphides or Plant-Lice. 



[APRIL. 



young are called " lice," and in a short time they resemble the 

 wingless parent, and can themselves produce living young. 

 This viviparous reproduction, where only females are present, 

 can go on for many generations. Should a plant be covered 

 with these Aphides, their food becomes scarce, and then they 

 have the power of producing winged females, which fly off to 

 other plants, and these deposit living young. Towards the end 

 of the year most Aphides produce males as well as females ; 

 these may be either winged or wingless. These females, after 

 being fertilised, deposit eggs at the base of buds and on the 

 stems, leaves, &c, of plants. These eggs remain over winter, 

 and hatch into the larvae that become the " Mother Queens " 

 with which this account of the life-history started. Some plant- 

 lice live entirely during the winter in the egg state (Bean, Pea, 

 Plum Aphis, &c), others mostly as insects, a few eggs only 

 occurring (Woolly Aphis). 



The effect of weather on Aphides is very great. Dry, hot 

 and sultry weather is favourable to them ; the same conditions 

 check the growth of the plant, and so the plant-lice soon 

 overcome it. An excessive quantity of manure, especially 

 nitrogenous manure, also predisposes the plant to Aphis 

 attack. 



Remedies. 



Aphides can easily be destroyed by spraying the affected 

 plants with a soft soap wash. This is made by dissolving from 

 6 to 10 lb. of soft soap in 100 gallons of soft water. The soft 

 soap blocks up the breathing pores of the plant-lice, and so 

 kills them. Quassia is sometimes added ; this acts as an 

 astringent to the leafage, and cleans it of the honey-dew and 

 excreta formed by the Aphides. For black-fly on Cherry, and 

 for all those that produce a copious flow of honey-dew, it is a 

 most useful ingredient. The quassia chips are boiled and the 

 extract added to the soft soap wash ; 6 to 8 lb. of .chips are 

 required to every ioo gallons of wash. Paraffin emulsion is 

 necessary for some kinds, as Woolly Aphis; which may also be 

 attacked in winter by caustic alkali wash (Leaflet No. 70). 

 For those which attack the root it is best to use bisulphide of 

 carbon injected into the soil, a quarter of an ounce to every 

 four square yards. Care must be taken with this substance, 



