144 INTRODUCTION 



As already explained in an earlier chapter (see p. 124) the colour-sense is 

 also particularly well developed in butterflies : there is certainly a remarkable corre- 

 spondence as to colour between some flowers atid the Lepidoptera which visit them. 

 Hernaann Miiller (Kosmos, iii, 1878, p. 418) gives the following additional examples 

 of this : The orange-hued Composites Crepis aurea, Hieracium aurantiacum, and 

 Senecio abrotanifolius, are a veritable playground in sunny weather for butterflies 

 of fiery-red colour (Argynnis Aglaja, Polyommatus Virgaureae, P, hippothoe var. 

 eurybia). Hermann Miiller saw the two copper butterflies (Polyommatus) in 

 question and Argynnis pales flying repeatedly even to the bright red fruits of Rumex, 

 and Blues (Lycaena) settling with unmistakable preference on the blue capitula 

 of the alpine species of Phyteuma. He is, therefore, inclined to think that the 

 same ' preference of butterflies for certain colours, as expressed in their own 

 adornment, which has been acquired hy sexual selection, has also determined their 

 choice of flowers, and therefore, indirectly, the colour of lepidopterid flowers, as 

 also the surprising resemblances existing between the odours of butterflies and 

 those of the blossoms they pollinate.' 



A case of protective resemblance described by E. Kohne (Verh. bot, Ver., 

 Berlin, xxviii, 1886, pp. 6-7) may be appropriately given here as a final illus- 

 tration of the above principle. This observer noticed, not far from Wangerin 

 in Pomerania, a very large number of male and female brimstone butterflies 

 (Rhodocera Rhamni Z.) on the pale capitula of the cabbage thistle (Cirsium 

 oleraceum L). In the position of rest the butterfly held its wings vertically, so 

 that their under-sides alone were visible, and these, especially in the rather whitish 

 female, harmonized so remarkably with the colour of the capitulum and its involucre 

 that when the light was bright not the slightest difference of hue could be perceived. 

 And it must be added that the involucral bracts project to some extent above the 

 capitulum, and that the shape of the resting butterfly, as determined by its pointed 

 wings, obviously simulates that of the upwardly directed points of the bracts. 

 Even the clear veining of the under-sides of the wings forciblj' reminds one of 

 that of the leaves. In fact, the form and colour of the capitula and involucres 

 agreed so closely with those of the butterfly, when seen in the glaring sunshine, 

 that Kohne could not distinguish with certainty, even from a very small distance, 

 whether or no a brimstone butterfly was resting on a given capitulum, and he 

 did not usually perceive the insect till it flew off on his approach. He regards 

 this remarkable colour-agreement between butterfly and plant as a mutual adaptation. 

 When on the wing, this butterfly, like most others, is protected from the attacks 

 of enemies by its erratic, undecided, devious flight ; if at rest it is never better pro- 

 tected than when it has settled on the yellowish capitulum. In places where 

 Cirsium oleraceum grows, it will therefore be able to maintain itself in large numbers, 

 and will consequently leave numerous offspring. The plant, on the other hand, 

 is assured of many visits from the insect, and hence of amply sufficient pollination 

 and seed-production. It too is, therefore, able to multiply to an unusual 

 extent. 



The significance of the individual groups of insects, with reference to the 

 pollination of flowers, has already t een dealt with by Hermann Miiller, who has 

 also given an exhaustive account of their structural peculiarities, so far as they are 



