| OCR Text |
Show 1887.] VALUE OF COLOUR AND MARKINGS IN INSECTS. 213 in producing a conspicuous appearance, although it may be admitted that the hairs do render subordinate assistance ; of the two remaining larvse, one is brightly coloured (O. antiqua), although the hairy tufts are in this case very important factors, while for S. menthastri no other suggestion except that of Jenner Weir has yet been made. In some of these larvse the effective colours are chiefly on the hairy covering, and the latter practically makes up the whole appearance. Furthermore in the last species there is evidence (Jenner Weir) that the insect is disliked for some quality other than the presence of hairs. It seems probable that the hairs of larvse possess irritating qualities to a much greater extent than is commonly supposed; but it is also likely that the hairy covering may be of direct value to the organism in other ways, some of which doubtless remain to be discovered. (Is it not likely that some tactile or other terminal organ of the nervous system may be in relation with hairs or bristles?) Of course it is well known that hairs are often exceedingly important in defending the insects by the converse method of a protective appearance (an extreme instance of this is afforded by the larva of Acronycta leporina, see Trans. Ent. Soc. Lond. 1886, pt. ii. June, p. 160). Prof. Meldola has kindly looked through the proof-sheets of this paper, and has suggested to m e that the probable original significance of the hairy covering was protection from injury after falling from the food-plant. The suggestion is strongly supported by the habits of the majority of hairy larvse. Any further considerations which arise out of the tables given above are better deferred until after an examination of similar instances in forms other than the larvse of Lepidoptera. II. Brightly coloured or conspicuous Insects (other than Larva). Under this heading I have only included such species as have been actually subjected to experiment. There are a very large number of additional species from many groups of insects which doubtless belong to this category ; but as they have never been brought to the experimental test, they are excluded from consideration on the present occasion. A n extended list will be found in Wallace's ' Contributions to the Theory of Natural Selection' already referred to (The essay on " Mimicry and other Protective Resemblances among Animals"). In most of the instances given by Wallace, we may feel confident that the test would prove satisfactory, especially as the author shows that in many cases the conspicuous form is mimicked by one or more species belonging to totally different groups, which accompany the former in its range and which, nearly always, keep in a small minority. Such facts render it in the highest degree probable (in fact make it nearly certain) that the mimicked species possesses some exceptional advantage in the way of inedibility or otherwise-some unpleasant peculiarity which confers upon it a more or less complete immunity from the attacks of the Vertebrate foes of its class. But in the present paper I am rigidly limiting myself to instances |
