PALATABILITY 



III 



many brightly-coloured larvae, such as the Cinnabar, Buff-tip, and large Cabbage butterfly. 

 I have myself to some extent confirmed these experiments with Lacerta viridis, which I found 

 would eat most green caterpillars, and also the inconspicuous larvae of T. pronuha, but 

 would only eat the larvae of P. brassicae with reluctance and when hungry. In 1887 Professor 

 Poulton contributed a paper to the Proceedings of the Zoological Society on ' The Experi- 

 mental Proof of the Protective Value of Colour and Markings in Insects in reference to 

 their Vertebrate Enemies ' . The experiments described were conducted with green tree-frogs 

 and various lizards, and the results are of the greatest importance, since the inquiry was 

 undertaken with the view of discovering how far the experiments would support (i) Wallace's 

 suggestion that brilHant and conspicuous larvae would be refused by some at least of 

 their enemies, and (2) the investigator's own suggestion that a limit to the success of this 

 method of defence would result from the hunger which the success itself tends to produce. 

 Putting the latter suggestion into other words, distasteful and conspicuous species might 

 be eaten, albeit with reluctance, under the stress of hunger caused by the distasteful 

 qualities themselves, such qualities thus becoming a limiting factor in the development of this 

 means of defence. The experiments went even further than this. It was sought to prove 

 the converse of Wallace's suggestion, viz. that all inconspicuous and cryptic forms would be 

 eagerly devoured. 



The details of the experiments are given in the form of tables which show in parallel 

 columns the results of all the tests made by Jenner Weir, Butler, Weismann, and Poulton. 

 Space does not permit of the reproduction of these exhaustive tables, but the results arrived 

 at are most conclusive. Some eighteen species of lepidopterous larvae, all very conspicuous, 

 were with one exception refused by some or all of the animals to which they were given, 

 except in cases where the latter were very hungry. Then the larvae were eaten with evident 

 compunction. The case of the larva of V. urticae was peculiar, as it was refused by birds 

 but eaten by lizards, showing, as might be expected, that protection against one enemy is 

 not always equally efficient against another. The distasteful qualities of the larvae of 

 A. grossulariata would seem to be exceptionally well developed. Frogs would taste them, 

 but always rejected them. A hungry lizard chewed one for some time and then rejected it. 

 Birds also refused them. Jenner Weir's diary contains a note on this species, to the effect 

 that a lizard which seized the larva immediately dropped it, afterwards licking its jaws as if 

 to remove the unpleasant taste, whilst another lizard rubbed its nose and mouth against the 

 moss after trying to eat one of these insects. Professor Poulton's further experiments on 

 the behaviour of insectivorous animals towards inconspicuous and cryptic insects, for the 

 most part supplied confirmatory evidence that such insects are readily eaten. The pupae of 

 Tryphaena pronuha were eagerly consumed by his lizards, and he points out that the imago 

 is much pursued and eaten by birds, a fact which I have myself frequently observed. It 

 may be interesting to note, as evidence of the keen struggle for existence experienced by this 

 species, that I have observed a female ovipositing while an earwig was eating the eggs as fast as 

 they were laid. The most striking result of these experiments is, however, that they demon- 

 strated the fact that some larvae, though exceedingly well concealed, nevertheless are highly dis- 

 tasteful. This phenomenon was illustrated in the case of the larva of Mania typica. It was 

 immediately attacked by a lizard, but rejected after being severely bitten, and other lizards 

 tasted the larva with the same result. As the author tells us, the young larvae, when hatched, 

 devour the upper cuticle and parenchyma of the leaf, leaving the lower cuticle entire, dry, 

 and brown. They lie closely packed side by side and apparently motionless, but in reality 

 gradually leaving a large brown space behind, thus adapting the surroundings to the brown 



