of its body, its
legs were used more, and its wings less, until they became incapable of
flight.

Kirby has remarked (and I have observed the same fact) that the anterior
tarsi, or feet, of many male dung-feeding beetles are very often broken
off; he examined seventeen specimens in his own collection, and not one had
even a relic left. In the Onites apelles the tarsi are so habitually lost,
that the insect has been described as not having them. In some other genera
they are present, but in a rudimentary condition. In the Ateuchus or sacred
beetle of the Egyptians, they are totally deficient. There is not
sufficient evidence to induce me to believe that mutilations are ever
inherited; and I should prefer explaining the entire absence of the
anterior tarsi in Ateuchus, and their rudimentary condition in some other
genera, by the long-continued effects of disuse in their progenitors; for
as the tarsi are almost always lost in many dung-feeding beetles, they must
be lost early in life, and therefore cannot be much used by these insects.

In some cases we might easily put down to disuse modifications of structure
which are wholly, or mainly, due to natural selection. Mr. Wollaston has
discovered the remarkable fact that 200 beetles, out of the 550 species
inhabiting Madeira, are so far deficient in wings that they cannot fly; and
that of the twenty-nine endemic genera, no less than twenty-three genera
have all their species in this condition! Several facts, namely, that
beetles in many parts of the world are frequently blown to sea and perish;
that the beetles in Madeira, as observed by Mr. Wollaston, lie much
concealed, {136} until the wind lulls and the sun shines; that the
proportion of wingless beetles is larger on the exposed Desertas than in
Madeira itself; and especially the extraordinary fact, so strongly insisted
on by Mr. Wollaston, of the almost entire absence of certain large groups
of beetles, elsewhere excessively numerous, and which groups have habits of
life almost necessitating frequent flight;--these several considerations
have made me believe that the wingless condition of so many Madeira beetles
is mainly due to the action of natural selection, but combined probably
with disuse. For during thousands of successive generations each individual
beetle which flew least, either from its wings having been ever so little
less perfectly developed or from indolent habit, will have had the best
chance of surviving