86 CHAPTERS ON EVOLUTION. 



be safest to look at the entire absence of the anterior tarsi (or feet) in 

 Ateuchus, and their rudimentary condition in some other genera, not 

 as cases of inherited mutilations, but as due to the effects of long-con- 

 tinued disuse ; for as many dung-feeding beetles are generally found 

 with their tarsi lost, this must happen in early life ; therefore the tarsi 

 cannot be of much importance, or be much used by these insects/' 



The beetles of Madeira present us with a remarkable state of 

 matters, which very typically illustrates how rudimentary wings may 

 have been produced in insects. Two hundred beetles, out of over 

 500 species known to inhabit Madeira, are "so far deficient in wings 

 that they cannot fly." Of twenty-nine genera confined to the island, 

 twenty-three genera include species wholly unable to wing their way 

 through the air. Now, beetles are frequently observed to perish when 

 blown out to sea ; and the beetles of Madeira lie concealed until the 

 storm ceases. The proportion of wingless beetles is said by Mr. Wollas- 

 tonto be "larger in the exposed Desertas than in Madeira itself;" whilst 

 most notable is the fact that several extensive groups of beetles which 

 are numerous elsewhere, which fly well, and which " absolutely require 

 the use of their wings," are almost entirely absent from Madeira. 

 How may the absence of wings in the Madeiran beetles be accounted 

 for ? Let Mr. Darwin reply : " Several considerations make me 

 believe that the wingless condition of so many Madeira beetles is 

 mainly due to the action of natural selection, combined probably 

 with disuse. For during many 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 from not being blown out to sea ; and, 

 on the other hand, those beetles which most readily took to flight 

 would oftenest have been blown to sea, and thus destroyed." An 

 instinct of laziness, so to speak, alone, or aided by a shortness of 

 wing, developed stay-at-home habits ; and such habits would 

 necessarily tend towards the survival and increase of wingless forms. 

 f N Other Madeiran insects 

 vvt^v suc k as butterflies, moths, 

 and flower- feeding beetles- 

 have well-developed wings, 

 or possess wings relatively 

 larger than they exhibit 

 elsewhere. This observa- 

 ;\ tion, remarks Mr. Darwin, 

 is quite in consistency with 

 the theory of the law of 



FIG. 25 .-SENT INE L CRAB. natural Selection which 



favours the survival of the 

 fittest. "For when a new insect first arrived on the island, the 



