LAWS OF VARIATION 123 



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 mutila- 

 tions are ever inherited ; and I should prefer explain- 

 ing 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 pro- 

 genitors ; 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, 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 considera- 

 tions 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 dis- 

 use. For during thousands of successive generations 

 each individual beetle which flew least, either from its 

 wings having been ever so little less perfectly de- 

 veloped or from indolent habit, will have had the best 

 chance of surviving from not being blown out to sea ; 

 and, on the other hand, those beetles which most 



