Appendix 



THE APHIS QUESTION 



Throughout the foregoing pages references have been made 

 to Aphids and their ways, but it is felt that the following 

 remarks on this particular insect may be of assistance in 

 combating them. 



As soon as a particular kind of weather becomes settled, the 

 great Aphis family make their annual bid for supremacy at 

 the expense of our food-crop. 



This well-kno\^^l but little understood insect is one of 

 creation's mysteries, and without going too deeply into the 

 subject it should be helpful to know something of its history. 



Ranging from a fiftieth to one-tenth of an inch only in size 

 and varying according to the species between black, green, 

 yeUow, red, brown, and combinations of these colours, aphids 

 afford pretty objects to the microscopist, and in their extreme 

 diversity of habits an absorbing study to the biologist, but 

 for all this the most that a grower will wish to know is how to 

 get rid of them. He may of course go so far as to inquire 

 " What good are aphids ? " 



For answer I would refer him to the pages of this book, 

 where I have pointed out how the obscure parasite has appar- 

 ently been " ruling the roost " though really engaged in 

 determining species, be it plant or animal. Growers will 

 readily agree upon reflection that it is the sappy, weak, 

 attenuated plants which aphids crowd on to most, whereas 

 hardy, sturdy plants resist attack. We need not however 

 carry our theory to the dangerous length of visualizing a great 

 Aphid C.-in-C. controlling his armies and despatching them 

 to the ends of the earth according to plan. The exact truth 

 is that the weakly, soft plants have been the means whereby 

 aphids have developed, and in the course of ages the numerous 

 species of plants have led to differentiation in the parasites 

 that affect them. 



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