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Show 194 MR. E. B. POULTON ON THE PROTECTIVE [Mar. 1, ose a great deal of blood, and although they may recover, are generally stunted ; and often I am sure the loss of blood proves fatal. If the wound be at all extensive, the fat-body and viscera protrude, owing to pressure on the side distal to the wound (that on the proximal side having been relieved by escape of blood)." Therefore it is that throughout the varied means of defence possessed by larvse " the object is always the same-to leave the larva untouched, a touch being practically fatal." Wallace also originally expressed this peculiar danger incurred by larvse in more general terms, viz. " their soft and juicy bodies are so delicate that if seized and afterwards rejected by a bird they would almost certainly be killed" (see ' Contributions to the Theory of Natural Selection,' 1875, p. 118). Other peculiar dangers of the larval stage will be pointed out below. Although it will be seen that brilliantly coloured and distasteful larvse are often tasted by their Vertebrate foes when impelled by hunger, all observers agree that a second trial is rendered less likely because of the unusual appearance which accompanies the unusual and unpleasant effect upon senses other than that of sight. Furthermore, I am now able to bring forward instances of very distasteful species which have no warning colours, but, on the other hand, are well disguised by protective tints and markings; and a comparison between the behaviour of Lizards towards these and the conspicuous species respectively, affords strong confirmation of the truth of Wallace's suggestion. It now remains to summarize the whole of the evidence in favour of the prediction made in 1867 ; for, after all, the question is purely one of evidence, and however convincingly the a priori arguments may be put, they are chiefly valuable as guides to practical investigation. And this is fully recognized by Wallace, who strongly urged the practical test upon the meeting at which his suggestions were first made. Experiments have been made by Mr. J. Jenner Weir, Mr. A. G. Butler, Prof. Weismann, and by myself. Jenner Weir (see Trans. Ent. Soc. Lond. 1869, part i., April) made use of the following birds in his investigations :-Erithaca rubecula (Robin), Emberiza citrinella (Yellow-hammer), Emberiza schceniclus (Reed-Bunting), Pyrrhula vulgaris (Bullfinch), Fringilla coelebs (Chaffinch), Loxia curvirostra (Crossbill), Turdus musicus (Thrush), Anthus arboreus (Tree-Pipit). He also used to a less extent Carduelis spinus (Siskin) and Linaria minor (Redpoll). He obtained the following results:- * "All hairy caterpillars (experimented upon) were uniformly uneaten ; " viz. Arctia caja, Eriogaster lanestris, Porthesia auriflua, and Orgyia anliqua. " None of these species were even examined." The writer believes that the hairs are not themselves disliked, but that they " serve as a caution to the birds that the larvse so clothed are uneatable." This suggestion is supported by the fact that the young and comparatively hairless larvse of Spilosoma menthastri were tasted by the Siskin, Redpoll, and by a West-African Finch (Textor erythrorhynchus), but these three birds evidently found the larvse disagreeable, and soon left them alone. On the other hand the |