Q74 STUDY OF NATURAL HISTORY. 
centipede, &c. Progression, however, among insects 
is not confined to flying, running, or swimming ; 
for although we lose sight of the leaping structure 
after quitting quadrupeds, we see this form again 
developed in the highest perfection both among the 
apterous (Aptera L.) and winged classes (Ptilota) ; 
of which the fleas in one, and the grasshoppers in 
the other, are examples occurring to every one. We 
cannot doubt, indeed, but that the saltatorial strue- 
ture is one of the primary types or models of nature, 
for she has produced it, under an infinite variety of 
forms and modifications, in almost every group of 
animals. Of this description is the hopping of some 
birds, in opposition to those which walk ; the hop 
being, in fact, but a short leap. Even among the 
Lepidoptera, where we should not expect to find any 
such analogous form, there are the Hesperide, 
which, from the sudden and peculiar quickness on 
the wing, have acquired the common but expressive 
name of Skippers. Not to mention the monilicorn 
tribe of beetles (under which we place the Chryso- 
melide of Linneus), where we have hundreds of 
little species, familiarly known to our farmers as 
fleas ; meaning thereby, a little black beetle of the 
same size, colour, and leaping in a similar manner 
to real fleas. A knowledge of all these habits, and 
of many others not alluded to, may be gained by 
induction, with almost as mueh certainty as if they 
were learned by experience. These inductions pro- 
duce higher conclusions ; and if these are confirmed 
by every thing we yet know, we arrive at a law of 
nature. That the saltatorial structure is one of those 
primary forms upon which all the variations of the 
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