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 us 

 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 very fre- 

 quently blown to sea and perish ; that the beetles in 

 Madeira, as observed by Mr. Wollaston, lie much con- 



