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Show 1887.] VALUE OF COLOUR AND MARKINGS IN INSECTS. 197 class, although one cannot be sure that there is not some smell, given off from the general surface of the body. It will be shown that in some cases it is even likely that larvse may be protected by their reputation for being indigestible. Again, the larvse may be disliked because of the possession of irritating hairs, as in the case of Porthesia auriflua, in which the effects of the hairs are almost immediate and intensely irritating (to man, and evidently to lizards &c.) ; or as in other hairy larvse which cause irritation after longer contact (e. g. Odonestis potatoria, from my own experience after long handling, and, as I hear from others, with Lasiocampa rubi and L. quercus &c.); but there is no doubt that the effects upon the delicate skin of the mouth would be much more rapid in all cases. W e also see that more than one unpleasant attribute may be present in a single larva, as in the case of P. auriflua, &c. Just as there may be many ways in which a larva may be unpleasant to its foes, there are many ways by which it may be rendered conspicuous, some of which have been suggested since Wallace's original hypothesis. Thus a larva may be conspicuous from its startling coloration (e. g. P. auriflua or A. grossulariata), or because it freely exposes itself, while its colours, although sober, do not harmonize with its food-plant (e. g. O.potatoria on grass, or B. rubi on heather). Again, it may become conspicuous by living in companies, in which case the individuals may be brightly coloured (e. g. C. neustria, E. jacobaa, P. bueephala, &c.) ; or may be sober-coloured, but strongly contrasted with the food-plant (e.g. the dark larvse of Vanessa io or V. urtiea, freely exposed in companies on the tops of nettles). It is obviously of less importance for the gregarious species to be as conspicuously coloured as the isolated larvse, because the numbers add greatly to the efficiency of comparatively sober colours. This explanation of the use of the gregarious habit in many species was made by Fritz Muller in ' Kosmos,' Dec. 1877, and an abstract of the paper was communicated to the Entomological Society of London bv Professor Meldola (see Proc. 1?*78, pp. vi & vii). The descriptions of appearance in all the tables are principally taken from Newman's works, the habits being chiefly described from my own experience. Prof. Westwood has most kindly assisted me in the search for the names of many of the species employed in the experiments. (See Table I., pp. 19W-203.) A second small group of larvse must be tabulated separately, i. e. those which take advantage of two methods of protection which at first si°-ht appear to be mutually exclusive-the method of protective resemblance and that of a conspicuous appearance, warning of unpleasant attributes. Such larvae are apt to pass unnoticed because of the harmony between their colours and markings and the artistic effect of their surroundings ; but if discovered, or even if an enemy approach so that there is danger of their being discovered, the protective attitude is instantly changed for one which renders the larva conspicuous and warns the enemy of the presence of unpleasant attributes (taste or smell), or alarms it by the resemblance of the new appearance to some object of terror. These facts may even be |
