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Show 1887.] VALUE OF COLOUR AND MARKINGS IN INSECTS. 239 can adequately appreciate the meaning of the colours and markings of any animal. III. Insects which evade their Enemies. We now come to Wallace's converse suggestion-that just as conspicuous forms which court observation will be avoided, so the insects which harmonize with their surroundings, and which evade their enemies, will be greedily eaten when detected and caught. I have adopted Meldola's suggestion that the terms " protective resemblance" should be applied to the appearances which tend to deceive enemies by their resemblance to motionless (vegetal or mineral) surroundings, the term "mimicry" denoting the resemblance to other animals. On entering upon the experimental investigation, I thought that I should have little to record except a complete agreement with everything which has been previously said upon the subject. I was surprised, however, to find some instances which are entirely antagonistic to the principles laid down by Wallace. Unfortunately the instances recorded by other observers are exceedingly few. Jenner Weir evidently experimented with a large number of species, but he gives very few details, and for the most part is content with summing-up his results as favourable, without exception, to Wallace's suggestion, in these words : - " I will now add a few words on those larvae which are eaten greedily by birds, and my remarks on the subject will be brief; it will be unnecessary to detail all the experiments made, as the results are easily generalized. " All caterpillars whose habits are nocturnal, dull-coloured, with fleshy bodies and smooth skins, are eaten with the greatest avidity. " Every species of green caterpillar is also much relished. " All Geometrae, whose larvae resemble twigs as they stand out from the plant on their anal prolegs, are invariably eaten They eat with great relish all smooth-skinned larvse of a green or dull-brown colour, which are nearly always nocturnal in their habits, or mimic the colour or appearance of the plant they frequent." Jenner Weir, however, gives details of experiments with other stages of Lepidoptera ; and I am now able to add many valuable details from his experiments upon Lizards in 1886. There are also a few instances to include from Mr. Butler's paper (already quoted) and a few of which I have beard from him by letter. In m y experiments I chiefly made use of the imagos of Lepidoptera, as I nearly alwavs sought for conspicuous larvae with which to test the suggestion previously discussed. Other observers having given so little detail, it follows that Wallace's converse suggestion possesses extremely little precisely recorded experimental foundation. There is, however, no reason to doubt that Jenner Weir's conclusions will be very generally confirmed by extended experiments, and they doubtless express the results of many observations. But as I have come across a few startling exceptions among the most protectively coloured forms, it is safer not |
