168 THE BOOK OF THE ROSE CHAP. 
of increase, and it is only in multitudes that they do 
any harm. In their anxiety to obey the command 
to increase and multiply, the presence of males is 
postponed as a useless luxury till the season is 
nearly over. In the meantime each individual, as 
soon as full grown, which will be in favourable circum- 
stances when about a week old, begins to produce 
young ones ready to commence juice-sucking at once, 
at the rate of dozens or so a day for weeks. In 
this manner it is said as many as seventeen gener- 
ations may be produced before the males appear, 
and it is calculated that the descendants of a single 
aphis in one season might thus be reckoned by 
millions. 
Strength, vigour, and cleanliness in the plants 
seem to be the best preventive measures. It may 
appear strange that vigour and health should keep 
off an insect foe, which we should fancy would be 
naturally congregated where there was the greatest 
abundance of sap for food, but though they are to 
be found on healthy plants, it will, I think, be 
generally allowed that the weaker ones are the most 
attacked. 
Destructive and remedial measures are many and 
various. Almost every insecticide known is adver- 
tised as destroying them; and no wonder, for they 
are delicate creatures with no power of escape, and 
are easily killed. The golden rule for all pests— 
attack the first symptons with immediate vigour— 
is especially applicable in this case. A constant 
look out, and crushing every one as soon as seen, 
never leaving it till to-morrow, is the remedy for 
aphides. 
Of all instruments and apparatus for the destroy- 
