324 Studies in the Theory of Descent. 



acquires undoubted protective colours cannot, 

 however, be classed with those which possess an 

 immunity from hostile attacks. 



That the coloured edges are correctly explained 

 as imitations of the oblique shadows of the leaf- 

 ribs, may also be proved from another point of 

 view. Let us assume, for the sake of argument, 

 that these coloured stripes are not adaptive, and 

 that they have not been produced by natural 



Europe (Germany, France, Hungary) the dark form is extremely 

 rare, in the south of Spain this variety, as I learn from Dr. Noll, 

 is almost as common as the yellow one. I hear also from 

 Dr. Staudinger that in South Africa (Port Natal) the dark form 

 is somewhat the commoner, although the golden-yellow and, 

 more rarely, the green varieties, occur there. I have seen a 

 caterpillar and several moths from Port Natal, and these all 

 agree exactly with ours. The displacement of the green (yellow) 

 form by the dark soil-adapted variety, appears therefore to 

 proceed more rapidly in a warm than in a temperate climate. 

 [Eng. ed. Dr. Noll writes to me from Frankfort that the 

 caterpillar of Acherontia Atropos in the south of Spain does 

 not, as with us, conceal itself by day in the earth, but on the 

 stems underneath the leaves. "At Cadiz, on the hot, sandy 

 shore, Solatium violaceum grows to a height of three feet, and 

 on a single plant I often found more than a dozen Atropos 

 larvae resting with the head retracted, It can easily be under- 

 stood why the lateral stripes are blue when one has seen the 

 south European Solanea } on which this larva is at home. 

 Solanum violaceum is scarcely green : violet tints alternate with 

 brown, green, and yellow over the whole plant, and between 

 these appear the yellow-anthered flowers, and golden-yellow 

 berries of the size of a greengage. Thus it happens that the 

 numerous thorns, an inch long, between which the caterpillar 

 rests on the stem, pass from violet into shades of blue, red, 

 green, and yellow."] 



