Xll 



Mr. Meldola stated that, with regard to the chemical aspect of the question, 

 he believed it possible for a poisonous substace derived from a food-plant to 

 permeate the tissues of a caterpillar without undergoing any change. The 

 evidence upon which this statement rested was to be found in the fact that 

 the colouring matters of some plants had been found by means of the 

 spectroscope in the tissues of larvae which fed upon them in an unaltered 

 condition. If colouring matters escape the digestive processes unaltered it 

 is probable that organic poisons would do the same. On the other hand, 

 it is well known that larvae feeding on non-poisonous plants may elaborate 

 poisons by chemico-physiological processes. The larva of Liparis auriflua, 

 which feeds upon hawthorn, sloe, apple, oak, &c., and which possesses the 

 well-known property of " urticating," was adduced as an example. 



Mr. M'Lachlan remarked that it was now generally admitted that the 

 urticating property was due to mechanical irritation, the numerous brittle 

 hairs of the larva entering the skin. 



Mr. Dunning and Mr. Waterhouse raised the question whether the hairs 

 thus penetrating the skin might not possess some poisonous quality. 



Mr. Meldola further remarked that he had observed that certain dis- 

 tasteful species of Lepidoptera preserved their disagreeable qualities after 

 death, in proof of which he exhibited some butterflies found among an old 

 collection of Indian insects, the greater part of which had been demolished 

 by mites. The surviving specimens were all of protected species, viz. four 

 of a Euploea, one of Danais plexippiLS, and one of Papilio Pammon. Euplosa 

 and Danais were well known to be protected genera, since they serve for 

 models of mimetic resemblance, \^'ith regard to Papilio Pammon, Mr. 

 Meldola stated that in his belief it was in some way distasteful, as he had 

 seen it in swarms in the island of Nancowry, Nicobar Islands, in April, 

 1875. 



Mr. M'Lachlan stated as a contrary fact that Cantharides is particularly 

 subject to the attacks of beetles. 



With regard to the means by which bright coloration might have become 

 associated with poisonous qualities in a larva, Mr. Meldola reminded the 

 Society of the experiments of Messrs. Jenner Weir and A. G. Butler, com- 

 municated to them in 1869. These gentlemen had pi'oved that brightly- 

 coloured, hairy and spiny caterpillars were generally distasteful, while dull 

 species were devoured. Mr. Wallace was of opinion that the observed 

 correlation between bright coloration, &c., and distastefulness was brought 

 about by means of Natural Selection. Mr. Meldola quoted the following 

 passage from Mr. Wallace's ' Contributions to the Theory of Natural 

 Selection ' : — " Distastefulness alone would, however, be of little service to 

 caterpillars, because their soft and juicy bodies are so delicate that if seized 

 and afterwards rejected by a bird they would almost certainly be killed. 

 Some constant and easily perceived signal was therefore necessary to serve 



