ETYMOLOGY. 
3 
ideas, we have only to turn to the mass of literature 
which relates to this subject, and notice how it embodies 
the labour of some of the most acute natural philo- 
sophers of almost every civilised country. 
The cause of this interest may be traced without 
difficulty to two principal facts. In the first place, 
the study of these creatures has presented to the 
embryologist questions for solution of the greatest 
importance. Phenomena connected with processes of 
reproduction occur, which even now some physio- 
logists consider to be abnormal, and concerning the 
interpretation of which unqualified consent is by no 
means accorded. 
In the second place, the general naturalist has 
found much to engage his earnest attention, whether 
he regards the varied life-history of the different 
species of Aphides, their curious habitations, the 
injuries they inflict on vegetation, or the defences they 
make against the host of insect foes which attack them 
on all sides — attacks which keep within limits an 
extraordinary fecundity, which otherwise might bring 
famine into the districts they infest. 
Professor Huxley quotes the following words of 
the enthusiastic savant Duvau : — J’ai souvent pense 
qu’on pourrait dans I’histoire des sciences designer les 
epoques par les principales decouvertes. Par exemple, 
1665 serait I’epoque de la Gravitation, 1789 Tepoque 
de la methode naturelle en Botanique, et, si 'parva licet 
componere magnis^ les annees 1740 a 1750 seraient 
I’epoque des Pucerons.” 
After such opinions no apology will be needed for 
setting forth those discoveries and ascertained facts 
which are connected with this division of the Hemipteea 
Homoptera. 
Before entering upon the general history of the 
British Aphides, it may not be considered out of place 
to devote a few remarks to the obscure etymology of 
the word Aphis. 
