VI PKEFACE. 



seem great, just as a shoemaker can make great shoes 

 for little feet." 



An attempt has been made so to blend the life-history 

 of Aphides with their morphology, as to render the 

 subject not wholly uninteresting to the general reader, 

 and yet to furnish details necessary for the systematist : 

 but the latter may reasonably ask that the facts shall 

 not be put before him in a form unnecessarily dry. 



The depths of Biology are as unfathomable as those 

 of any other science. The long list of authors I 

 furnish at the end of this volume, though far from 

 exhaustive, will show how much attention has been 

 already paid to this group of insects ; and yet I am 

 sensible of many omissions, and that much has yet to 

 be discovered with reference to my subject. It would 

 almost seem that more may be written on this one 

 single insect family than on the life-history of a family 

 of the carnivorous Vertebrata ; — we may instance the 

 Felida3. Indeed, several years' study is required to pro- 

 duce a complete life-history of some insects, and they 

 may require special treatises to exhaust the subject. 



Through the kindness of M. J. Lichtenstein, I am 

 enabled to give a short but compendious history of the 

 grape-vine pest, Phylloxera vastatrix. His researches 

 and familiarity with the whole tribe will make his 

 observations acceptable to all. 



Although not strictly within the province of a treatise 

 on British Aphides, a chapter has been devoted to the 

 question of the general existence of Aphides in early 

 geological times. The author has freely consulted 

 several important memoirs of Prof. Oswald Heer, and 

 also his valuable treatise on the ' Primeval World of 

 Switzerland.' .Much help lias likewise been obtained 



