APPENDIX. 373 



hold in corporeal structures, namely, that tlie parts which 

 differ most in allied species, are apt also to vary most in the 

 same species. Another Bee, the Megachilc maritirna, as I am 

 informed by Mr. Smith, near the sea makes its burrows in the 

 sand-banks, whilst in wooded districts it bores holes in posts.* 



I have now discussed several of the most extraordinary 

 classes of instincts ; but I have still a few miscellaneous 

 remarks which seem to me worth makinj^. First for a few 

 cases of variation which have struck me : a spider which had 

 been crippled and could not spin its web, changed its habits 

 from compulsion into hunting — which is the regular habit of 

 one large group of spiders.f Some insects have two very 

 different instincts under different circumstances, or at different 

 times of life ; and one of the two might through natural selec- 

 tion be retained, and so cause an apparently abrupt difference 

 in instinct in relation to the insects' nearest allies : thus the 

 larva of a beetle (the Cionus scroijhularice), when bred on the 

 scrophularia, exudes a viscid substance, which makes a trans- 

 parent bladder, within which it undergoes its metamorphosis ; 

 but the larva when naturally bred, or transported by man, on 

 to a verbascum, becomes a burrower, and und(;rgoes its meta- 

 morphosis within a leaf.| In the caterpillars of certain moths 

 there are two great classes, those which burrow in the paren- 

 chyma of leaves, and those which roll up leaves with consum- 

 mate skill : some few caterpillars in their early age are 

 burrowers, and then become leaf -rollers ; and this change was 

 justly considered so great, that it was only lately discovered 

 that the caterpillars belonged to the same species. § The 

 Angoumois moth usually has two broods : the first are 

 hatched in the spring from eggs laid in the autumn on grains 

 of corn stored in granaries, and then immediately take Hight 

 to the fields and lay their eggs on the standing corn, instead 

 of on the naked grains stored all round them : the moths of 

 the second brood (produced from the eggs laid on the standing 

 corn) are hatched in the granaries, and then do not leave the 

 granaries, but deposit their eggs on the grains around them ; 

 and from these eggs proceed the vernal brood which have the 



* [Here follows a section on the instincts of Parasitism, Slave-making, and 

 Cell-making, which is published in the Orifjia of Species. — Gr. J. E,.] 

 t Quoted on authority of Sir J. Banks in Journal Linn. Soc. 

 X P. Huber in Mem. Soc. Phi/s. de Geneve, tome x, p. 33. 

 § West wood, in Gardeners' Chronicle, 1852, p. 261. 



