102 Mr. W. L. Distant's Geographical Distribution 



casual escape from gardens.* This introduced plant at 

 the Azores, now apparently establishing its habitat, wiU 

 be one of the most favourable conditions to D. Archippus 

 surviving in the same locality ; and it would be deeply 

 interesting to know whether that butterfly has again 

 appeared or established itself at the Azores since the visit 

 of Mr. Godman. 



2ndly. Its immunity or protection from the attacks of 

 birds, S^c. — In its larval condition it has been found by 

 Mr. Riley to be refused by turkeys, chickens, toads or 

 snakes ; and this has been ascribed to the odour, which, 

 scarcely appreciable when the larvge are in the open air, is 

 pungent and nauseous in the extreme Avhen a few of them 

 are shut up a short time in a tight box.f May not this 

 probably be from the nature of its food plant ? Most of the 

 species of the genus Asclepias possess powerful medicinal 

 properties, especially the roots of A. curassavica. Its gay 

 colour is likewise considered a protection ; but if we look 

 at the fleshy processes or horns of tlie larva as also pro- 

 tective, we shall find that it compares unfavourably in that 

 respect with the larvge of D. Plexippus and Chrysippus 

 as figured by Horsefield and Moore, and D. Berenice as 

 figured by Boisduval and Lecomte, all of which species 

 have three pairs of these fleshy processes, whilst D. 

 Archippus has but two. The larva only obtains its 

 bright colours slowly, or rather they become developed as 

 it increases in growth ; hence upon the hypothesis of colour 

 protection we should have expected the larva to have had 

 the same immunity in its younger stages, or else the 

 theory must break down. But for this there remains 

 another contingency, as, fi:om Mr. Riley's description of 

 the young larva, it is covered with minute black bristles 

 arising from still more minute warts; and as we know 

 that most hairy caterpillars are likewise the rejected of 

 birds, it seems in this case that the young larv^, though 

 obscurely coloured, are as much protected by their hairy 

 coats as they are later on by a totally different and more 

 showy exterior. It is also protected in the perfect condi- 

 tion probably by the same odour which affords its larvaa 

 immunity from the attacks of birds, &c. It is unnecessary 

 to descant upon the extreme importance of this protection, 

 as the absence of insectivorous birds, or an immimity from 



* Nat. Hist, of the Azores, p. 194. 



t Third Ann. Rep. of Ins. of Miss. p. 149. 



