4J6 SYSTEM OF INSECTS, 



mediate direction, it matters not), it cannot be satisfac- 

 torily ascertained but by considering attentively the gra- 

 dual approximation or recession of the structure to or 

 from a certain type in any point of such series. If, there- 

 fore, you wish to ascertain whether the characters, in 

 which any given object resembles other objects in certain 

 groups, indicate affinity "or only analogy, you must first 

 makeyourself acquainted with the common features which 

 distinguish the animals known to belong to that group, 

 either those relating to their structure, or to their 

 habits and economy. If the object under your eye par- 

 takes in these characters more or less, in proportion as 

 it approaches the type or recedes from it, the relation it 

 exhibits is that of affinity; but if, though it resembles 

 some members of it in several points of its structure, it 

 differs from the whole group in the general features and 

 characteristic marks that distinguish it, the relation it 

 bears to those members is merely that of analogy. Thus, 

 for instance, Ascalaphus italicus in its antennaa, the co- 

 louring of its wings, and its general aspect, exhibits a 

 striking resemblance to a butterfly / yet a closer examina- 

 tion of its characters will satisfy any one that it is in quite 

 a different series, and has no affinity whatever to that 

 genus. A departure, however, in only one respect from 

 what may be called the normal characters of its group, 

 does not annul the claim of any tribe of insects to remain 

 in it; since this very often only indicates a retrocession 

 from the type, and not a disruption of its ties of affinity. 

 Thus the saw-flies (Serrifera} differ from the other Hy- 

 menoptera, though not in their pupas, yet more or less 

 in their larvae ; but this alone cannot countervail their 

 agreement with that Order in their organs of manduca- 



