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Show 238 MR. E. B. POULTON ON THE PROTECTIVE [Mar. 1, forms also probably gain to some extent by the greater publicity which follows from the resemblance. W e therefore see that the force which tends towards the acquisition of similar forms of colour and marking in widely different organisms is itself the resultant of other forces varying in relative amounts in the different species. Of these primary forces we have been enabled to detect two in the majority of cases, and three in the minority, i. e. (1) The feasibility of certain colours and patterns depending upon their effect on the vertebrate eye, and thus giving the enemies as easy an education as possible ; (2) The advantage of facilitating the education of enemies by giving them a small number of patterns and colours to learn ; and (3) The great additional advantage conferred by trading upon the reputation of a well-known and much-feared or much-disliked insect. These may probably be looked upon as the chief primary forces which have determined the various forms of conspicuous appearance. But such forces have had very different material to work upon in the different species, and doubtless the resultant has been largely influenced by the protective colours which existed before the" warning" colours and markings arose, and which formed the material on which the first steps (at any rate) were built. W e can, in fact, point to certain conditions in the "warning" appearance of some species which are almost certainly remnants of a previous mode of defence due to protective coloration. Thus Prof. Meldola has drawn my attention to an opinion expressed by Mr. T. W . Wood (" Insects in Disguise," Student, 1868), that the larvae of E. jacobaa are protected by their resemblance to the flowers of the ragwort. I believe that in tbe orange ground-colour of this species we have such a remnant of a former resemblance to the flowers of this plant and the groundsel, on which the species also feeds. The acquisition of the black bands and, above all, the gregarious habits are, then, later developments which have followed the acquisition of an unpleasant taste. Here it is seen that the material at the disposal of the primary forces tending towards a " warning" appearance was such as to render most probable the resultant which has actually obtained. Again, Mr. Thomas Eedle informed Prof. Meldola that he believed the larva of C. verbasci resembles the flowers of its food-plant, mullein. Here, again, I entirely agree with this observation. There is a great deal in the larva which harmonizes extremely well with the yellow and dark sessile flowers, studded upon the surface of the thick green spike, and surrounded by green unopened flowers. In this case it is probable that the pattern may have been rendered a little more distinct; but the very conspicuous appearance practically depends upon the gregarious habit, and upon the fact that the larvse do not chiefly rest upon the spike, but are commonly seen upon the uppersides of the large leaves, forming a background against which the larval colours appear with startling distinctness. But, as Mr. Eedle maintains, an isolated larva on the flowering-spike is evidently well protected by colour-harmony with its surroundings. These are but instances of the past history which must be deciphered before we |