210 MR. E. B. POOLTON ON' THE PROTECTIVE [Mar. 1, 



distasteful species are carefully excluded from the diet. Thus 

 Butterflies and Moths are freely eaten by Lizards (see Appendices) ; 

 but I am sure that they are not really enjoyed in the same way as 

 when a Housefly or a palatable Caterpillar is offered to them. This 

 is doubtless because the imagos of Lepidoptera are dusty, unsatis- 

 factory things to eat, with such a small proportion of body in 

 which the real nutriment and taste is contained, and so large an 

 expanse due to the dry membranous wings with their scaly 

 covering. In this respect the Butterflies contrast unfavourably (as 

 food) with the Moths, and the latter are certainly preferred (when 

 both are palatable in other ways). The same preference is manifested 

 bv Fiogs {Hyla nrborea) with even greater force ; there is a most 

 extraordinary difference in the behaviour of such a Frog in the 

 presence of a Housefly or of a Butterfly respectively, and in fact the 

 latter is often disregarded. Of course birds are in a different position 

 as regards such insect-food, for they at any rate very generally 

 pick off the unpalatable parts before eating a lepidopterous imago 

 (Jenner Weir) ; and with them it is common to witness all the signs 

 of an intense desire for these insects, especially Moths. Birds can 

 similarly' largely remove the un[)leasanlness due to larval hairs, as 

 was seen in the case of 0. antiqua (Table 1.). We should doubt- 

 less see evidence lor the existence of such nice discrimination 

 between the relative palatabilities of various insects, in the case of 

 all insect-eaters, if our observations were sufficiently numerous and 

 minute ; but it must be quite clear that the preferences cannot 

 be always satisfied, when we remember the extent and keenness of 

 competition. In this country it is hard to realize the excessive 

 abundance of reptile life, chiefly among the Lizards, which obtains 

 even so near to us as the south of Europe, and which almost entirely 

 depends upon the insect fauna for food. Almost every step along 

 an Italian road startles several Lizards on the road-side wall or bank ; 

 and it must be perfectly clear that under such circumstances it is 

 quite impossible for all to be served with the food which is most 

 appreciated. We see rather the very conditions which must render 

 the acquisition of an unpleasant taste together with the correlative 

 "warning" colours, an exceedingly hazardous mode of protection, 

 if assumed by more than a small propoition of the species constituting 

 the insect fauna of such a country. For in so great a press of 

 competition among the innumerable insect-eaters, we may feel sure 

 that some at least would be sufficiently enterprising to make the 

 best of unpleasant food, which has at least the advantage of being 

 easily seen and caught. And such a conclusion will, 1 think, be 

 confirmed by a study of the tabidated details. It must be admitted 

 th;it Wallace's suiigestion, with its experimental proof, has taken a 

 most important place among the principles which deal with the 

 infinitely complex and ever-changing relations which obtain between 

 the most widely separated no less than between the most allied 

 members of the organic kingdom. But it is no less true that tlie 

 principle carries with it its own compensating principle, which will 

 come into operation precisely as the former advances to the possession 



