KHIZOBIIN^]. 79 



INTRODUCTION. 



Classification is based on certain observed affinities 

 and agreements with types, or divergencies therefrom. 

 In proportion as a grouping of animals accords with 

 their biology, morphology, and the like, will any 

 given arrangement assume a scientific value. It is, 

 however, obvious that all classifiers do not attach 

 equal value to the same characters. A consensus of 

 opinion, however, will render any schemes they may 

 raise more likely to be in accordance with natural 

 laws. 



Genera, however, may be temporally adopted for 

 mere convenience and a means of study, until such 

 time as a better acquaintance with embryology and a 

 true phyllogeny will permit a more perfect grouping. 

 These remarks will more particularly apply to the 

 tribe immediately following. 



Perhaps of all divisions of the family Aphidiuse 

 no group presents so great difficulties in classifi- 

 cation as that which Passerini has marked under 

 the sectional name of RhizobiinEe. The fossorial 

 habit shown by all the known species, and their 

 attachment to the young roots of various plants, 

 is by no means confined to Aphides of this 

 tribe. We have noted subterranean habits in Sipho- 

 nophera, Aphis, Pemphigus, Schizoneura, Paracletus, 

 and Trama, therefore the meaniug of the term is not 

 exclusive, as a generic term should be. Linnseus's 

 well-known words, " Nomina si nescis, perit et cognitio 

 rerum," may go too far; but a name is a first step 

 towards an exact knowledge of a thing. It may be a 

 question whether the names of genera should ever 

 express or involve an hypothesis. 



Burmeister described a species which burrowed at 



