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AFRICAN MIMETIC BUTTERFLIES 



colour of the larvae. The gregarious habits are subordinated to cryptic ends, affording 

 a peculiar method of concealment for the young larvae. After a time, being too large to be 

 further concealed in this manner, they descend and feed on low-growing plants. After 

 hibernating they begin feeding again in the spring, always carefully concealing themselves 

 by day, hiding themselves in the folds of brown leaves and in dark corners. In spite of 

 the fact that the larva behaves in the same manner as those which are very palatable, and 

 therefore must hide from their enemies, it obviously possesses a very nauseous taste and 

 probably smell. The lizard recognized it as something which was expected to be palatable, 

 and it was only after severely biting it that the nauseous taste became evident. Thus we have 

 nauseous qualities present in a larva as an entirely useless attribute, a discovery of the 

 greatest importance^ for here at once is a possible explanation of the manner in which distasteful 

 qualities may have arisen and become coupled with warning coloration. The distastefulness 

 is there incidentally and should the struggle for existence become so severe as to cause the 

 larva in its hiding-place to be more carefully sought by its foes, we can easily understand 

 how selection, acting on variation, might develop a pattern which would be conspicuous 

 and easily recognized, thus causing a change in the creature's mode of defence. It is further 

 pointed out by the author of the experiments that there is no known instance of an insect 

 being distasteful in the imago state when the larva is edible, showing that the distasteful 

 qualities have evidently arisen in the larval stages. This is certainly what we should expect, 

 since the nauseous juices are probably elaborated from the food plant, and thus passed on to 

 the pupa and imago. The author gives a list of special conclusions which may be drawn from 

 the results of the foregoing experiments. Those bearing directly on the present subject are — 



1. Highly conspicuous insects nearly always possess some unpleasant attribute, i.e.. 

 a disagreeable taste or smell in the tissues or fluids of the body, or (in the case of the smell) 

 discharged from special glands : irritating hairs or stings. 



2. In a small number of cases a highly conspicuous appearance has not yet been shown 

 to be attended by any unpleasant attribute. 



3. The likes and dislikes of insect-eaters are purely relative, and if pressed with hunger 

 the most disagreeable and highly conspicuous insects may be eaten. Hence probably the 

 relatively small number of species which adopt this mode of defence. 



4. In a very small number of species the most perfect form of protective resemblance 

 may coexist with a most unpleasant taste. 



It was in the hope of making some further discoveries in regard to the edibility of larvae 

 that I undertook in the summer of 1909 some experiments with lizards. A species of green 

 lizard, probably Lacerta viridis, was utilized for the purpose, and my results were com- 

 municated to the Entomological Society in October of that year. Generally speaking, 

 the results confirmed those of previous experimenters. Green larvae and all those which 

 were inconspicuous, and for the most part night feeders, were eagerly devoured. Blue- 

 bottles and other flies were always relished. Once a bee was seized, but the lizard was evidently 

 stung as it dropped the insect hurriedly. The most interesting result was obtained with the 

 larva of the Geometrid moth Odoniopera hidentata. This larva is probably better pro- 

 tected by a cryptic appearance than almost any other British species. I found it feeding 

 on ivy, and so perfect was the resemblance of the caterpillar to the ivy twigs that in many 

 cases it could only be detected by the sense of touch. Nevertheless my lizards found it 

 extremely distasteful. They would seize the larva and drop it again with every sign of 

 disgust. They rubbed their noses on the gravel at the bottom of the cage, and in one case 

 a lizard which had had no food for some days apparently managed to swallow the caterpillar. 



