LOCAL AND SPECIFIC VARIETIES OF INSTINCT. 255 



particular species or genus in question, after that species or 

 genus had branched off from the more ancestral type. Now 

 such cases of specific instinct are by no means rare — cases, 

 I mean, like that of the California!! Woodpecker (Mclancrpcs 

 formicivorus), which displays the curiously distinctive instinct 

 of storing acorns in the crevices of the bark of the yellow 

 pine (Pinus pondcrosa) for future food, while no other species 

 of woodpecker shows ony tendency to such a habit.* But 

 such cases of instinct peculiar to one species or genus are so 

 common that I feel it would be needless to enumerate them, 

 in view of the more conclusive cases just given — cases more 

 conclusive because the obsolete instincts happen to have been 

 of a kind requiring special corporeal structures for their 

 operation, which now survive their ancestral uses.t Lastly, 

 wc must not forget the important fact that we are far from 

 being wholly without evidence of the transmutation of instinct 

 taking place under actual observation — as in the case of the 

 ducks in Ceylon having quite lost their natural instincts 

 with regard to water (in this resembling the upland geese), 

 sparrows and swallows building on houses instead of on trees, 

 insects, birds and mammals which normally feed on vegetable 

 substances suddenly becoming carnivorous, &c, &c. ; for all 

 these cases of local varieties of instinct are really so many 

 cases of racial varieties, and the step between this and specific 

 varieties is clearly not a large one. 



* According to Mr. C. J. Jackson (Proc. Boston Nat. Hist. Soc, vol. x, 

 p. 227) the acorns selected for storing arc only those which are infested with 

 maggots, which serve as food for the young in the following spring ; and the 

 acorns arc driven into holes specially prepared for them, and which fit so 

 well that the maggots when th--\ come to mat urity are unable to escape — 

 being therefore imprisoned in a larder until they are required for the use of 

 the young birds. See also J. K. Lord's Naturalist in I'ancouvers Island, 



vol. i. pp 288-02, and Thelbu, L868. 



T The most suggestive of this class of cases are those in which the species 

 which exhibits the instinct peculiar to itself happens to have become dis- 

 persed hut wide geographical areas since the instinct arose, and being there- 

 fore now found m different parti of the world, living under different, 

 conditions of life, and yet retaining the same peculiar instinct. Thus, for 

 instance, " in all quarters of the globe species of trap-door spiders arc found 

 occurring in more or less localized areas," and the harvesting ant- of Europe 

 and America belong to the same genus. The South Ainerieun Thru-h Inns 



ith nesl with mud in the same wa\ as does our own Thrush, the Bornbills of 

 Africa and of [ndis in their oidiflcation shon the same peculiar instinct of 

 imprisoning their hens in hobs of trees with plaster, &o., ao. 



