140 EFFECTS OF USE AND DISL'SE. Chap. V. 



of prey, lias been caused by disuse. The ostricli, indeed, in- 

 Imbils continents and is exposed to dann^er from -wliicli it cannot 

 escape by llii^^lit, but by kickinp^ it can defend itself from ene- 

 mies, as well as any of the smaller ciuadrupeds, "We may be- 

 lieve that the progenitor of the ostrich fj^enns had habits like 

 those of a bustard, and that, as natural selection increased in 

 successive g-enerations the size and weight of its body, its legs 

 were used more, and its wings less, until they became incapa- 

 ble 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 spe- 

 cimens in his own collection, and not one had even a relic left. 

 In the Onites apclles the tarsi are so habitually lost, that the 

 insect has been described as not having them. In some other 

 genera they are present, but in a rudimentary condition. In 

 the Ateuchus or sacred beetle of the Egyptians, they are totally 

 deficient. The evidence that accidental mutilations can be in- 

 herited is at present not quite decisive ; but the remarkable 

 case observed by Brown-Sequard of inherited epilepsy in guinea- 

 pigs, caused by an operation performed on the spinal cord, 

 should make us cautious in denying such power. Hence it 

 Avill ]>ei]iaps be safest to look at the entire absence of the an- 

 terior tarsi in Ateuchus, and their rudimentary condition in 

 some other genera, as due to the effects of long-continued 

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

 with their tarsi lost, this nnist happen earlv in life; therefore 

 tlie tarsi cannot be of much impoi'tance or be nnich used by 

 these insects. 



In some cases we might easily put do"^^'n to disuse modifi- 

 cations of structure which are wholly, or mainly, due to natural 

 selection. Mr. AYollaston has discovered the remarkable fact 

 that ::300 beetles, out of the 550 species (but more are now 

 known) which inhabit Madeira, are so far deficient in wings 

 that they cannot fly; and that, of the twent^'-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. AVollaston, lie 

 much concealed, until the wind lulls and the sun shines ; that 

 the ])roportion of wingless beetles is larger on the exposed 

 Desertas than in Madeira itself; and especially the extraor- 

 dinary fact, so strongly insisted on by Mr. AVoUaston, of the 



