LAWS OF VARIATION 195 



of the twenty -nine endemic genera, no less than twenty- 

 three 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 con- 

 cealed, 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 ex- 

 traordinary fact, so strongly insisted on by Mr. Wol- 

 laston, that certain large groups of beetles, elsewhere 

 excessively numerous, which absolutely require the use 

 of their wings, are here almost entirely absent; — these 

 several considerations make me believo that the wingless 

 condition of so many Madeira beetles is mainly due to 

 the action of natural selection, combined probably with 

 disuse. For di ring manj successive generations each in- 

 dividual 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. 



The insects in Madeira which are not ground-feeders, 

 and which, as certain flower-feeding coleoptera and lepi- 

 doptera, must habitually use their wings to gain their 

 subsistence, have, as Mr. Wollaston suspects, their wings 

 not at all reduced, but even enlarged. This is quite 

 compatible with the action of natural selection. For 

 when a new insect first arrived on the island, the ten- 

 dency of natural selection to enlarge or to reduce the 

 wings would depend on whether a greater number of 



