PALATABILITY 



113 



A moment afterwards, however, it ejected it and ran violently round the cage, finally 

 drinking some water. In the course of a great number of trials the larva was actually eaten 

 on one or two occasions, but usually under stress of hunger or competition. Once two lizards 

 seized the same larva, which was pulled in two in the fight which ensued, and each lizard 

 consumed its own half. That such competition has some effect was shown by the fact that 

 on another occasion a lizard seized one of the larvae and, on putting it out, another lizard came 

 to inspect it. The first lizard immediately picked up the larva again and ran away with it. 

 It subsequently put it out again. Though it could not eat it, it would not give it up to the other. 



Having satisfactorily proved the distastefulness of the insect, it occurred to me to try 

 the effect of a change of food plant. Several larvae were placed upon apple leaves, which 

 they readily consumed. After this diet had been continued for a few days, the caterpillars 

 were again presented to the lizards, when they ate them without the slightest hesitation. 

 Though the experiment was repeated again and again, on no single occasion was an apple-fed 

 larva refused after being once tasted. This experiment, while discovering a case similar to 

 that of M. typica, above described, also showed that if a larva were capable of changing its 

 food plant, it might also undergo a great change in its edible qualities. An interesting light is 

 thus thrown on a peculiar natural development. An insect which had hitherto escaped its 

 enemies by its cryptic habits and coloration might be ultimately sought out by its foes, 

 and if the latter were sufficiently numerous and persistent, they might cause its extermina- 

 tion. Some few might, however, survive for the time being on another food plant which 

 unexpectedly gives them nauseous qualities ; and, as in the case of M. typica, makes possible 

 the development of conspicuous colours, and what was once an edible cryptic larva might 

 thus quite conceivably become a warningly-coloured distasteful species. At least the 

 supposed difficulties of those first stages in the development of distastefulness are, in the 

 light of these results, further considerably minimized, since, other factors being equal, 

 the slightest variation towards conspicuousness would now assist the larva in the struggle 

 for life. The question may very properly be asked whether the moths resulting from ivy- 

 fed larvae are distasteful, and those from apple-fed larvae palatable. This question I am 

 as yet unable to decide, but though deeply interesting the reply would not greatly affect 

 the argument, since distasteful qualities must arise first in the larva, and that is the only 

 stage in which their origin presents a difficulty.'- 



We may now proceed to consider experiments which have been made abroad with a view 

 to testing the degree of edibility of butterflies and other insects. M. de Niceville experimented 

 with a common species of mantis and found that whilst it ate most of the butterflies which 

 he gave it, it always refused Acraea violae. Mr. Frank Finn, Deputy Superintendent of the 

 Indian Museum, made numerous experiments in 1895, 1896, and 1897, with Indian birds 

 and lizards, by feeding them with butterflies. The results of these experiments showed 

 that while the lizards did not show very much discrimination, the birds, though in many 

 cases eating the distasteful kinds, showed on the whole a good deal of preference for the 

 non-warningly coloured species. At the conclusion of the account of his 1895 experiments 

 Mr. Finn says, ' these experiments left not the slightest doubt in my mind as to the un- 

 palatability of Danais and the other " warningly-coloured " forms. Birds would often only 

 look at them, and soon left them when picked up ' (Journ. Asiatic Soc. of Bengal). 



1 Since the above was written three of the moths small number of moths were available it seems reason- 

 have been hatched out and presented to lizards and able to suppose that the distastefulness of the larva 

 a bird {Graculifica melanoptera). The insects were is not continued in the imago. The moths are e.x- 

 eaten without any signs of distaste. Though such a tremely cryptic and resemble leaves. 

 1200 p 



