Chap. V. 
USE AND DISUSE. 
135 
quadrupeds. We may imagine that the early progenitor 
of the ostrich had habits like those of a bustard, and 
that as natural selection increased in successive genera¬ 
tions the size and weight 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 pre¬ 
sent, but in a rudimentary condition. In the Ateuchus 
or sacred beetle of the Egyptians, they are totally defi¬ 
cient. 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 ante¬ 
rior 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. 
