I next made the experiment of placing before a lizard a caterpillar as much as possible like that of _E. Jacobææ_. Half grown larvæ of _Bombyx Rubi_ likewise possess golden yellow (but narrower) transverse rings on a dark ground, and they are much more hairy than those of _E. Jacobææ_. The lizard first applied its tongue to this caterpillar and then withdrew it, so that I believed it would also be avoided; nevertheless it was subsequently eaten. The caterpillars of _Saturnia Carpini_ were similarly devoured in spite of their bristly hairs, and likewise cuspidate larvæ (_Dicranura Vinula_), notwithstanding their extraordinary appearance and their forked caudal horn.[152] These lizards were by no means epicures, but consumed large numbers of earth-worms, slugs, and great caterpillars, and once a specimen of the large and powerfully biting Orthopteron, _Decticus Verucivorus_. Creatures which possessed a strongly repugnant odour were, however, always rejected, this being the case with the strongly smelling beetle, _Chrysomela Populi_, as also with the stinking centipede, _Iulus Terrestris_, whilst the inodorous _Lithobius Forficatus_ was greedily eaten. I will call particular attention to these last facts, because they favour the supposition that with rejected caterpillars a disgusting odour--although perhaps not always perceptible by us--is the cause of their being unpalatable. Striking colours are of course only signals of distastefulness, and the experiment with _Bombyx Rubi_ shows that the lizards were from the first prejudiced against such larvæ, the prejudice only being overcome on actually trying the specimen offered. A subsequent observation which I made after arriving at this conclusion, is most noteworthy. After the lizard had learnt by experience that there might be not only distasteful caterpillars (_E. Jacobææ_), but also palatable ones banded with black and yellow (_B. Rubi_), it sometimes tasted the _Jacobææ_ larvæ, as if to convince itself that the insect was actually as it appeared to be, viz., unpalatable! A striking appearance combined with a very perceptible and penetrating odour is occasionally to be met with, as in the caterpillar of the common Swallow-tail, _Papilio Machaon_. I have never seen a lizard make the slightest attempt to attack this species. I once placed two large specimens of this caterpillar in the lizard vivarium, where they remained for five days, and finally pupated unharmed on the side of the case. I have recorded these experiments, although they do not thus far relate to Sphinx-caterpillars, with the markings of which we are here primarily concerned, because it appeared to me in the first place necessary to establish by my own experiments that signals of distastefulness did occur in caterpillars. I now come to my unfortunately very meagre experience with _Deilephila_ larvæ, with only two species of which have I been able to experiment, viz., _D. Galii_ and _Euphorbiæ_.