406 SYSTEM OF INSECTS. 
various instances of the latter that occur between insects 
and other animals, and betweeen different tribes of in- 
sects themselves. 
To know what characters denote affinity and what 
are merely analogical, it must be kept in mind that the 
former being predicated of beings in a series (whether 
that series has its gyrations that return into themselves, 
or proceeds in a right line, or assumes any other inter- 
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 
make yourself 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 antenne, 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 diflerent series, and has no affinity whatever to that 
