1896. NOTES AND COMMENTS. 231 



genus. The species of Diahrotica are among those successful forms of 

 insect-life that make even the entomologist sympathise with the 

 feeling of the outsider who concludes that it is a great mistake on the 

 part of Nature to have so many kinds of insects. There are hundreds 

 of species of Diahrotica : usually they are very pale green or yellow 

 beetles, shining with conspicuous black marks, and some, if not all of 

 them, are believed to be nasty to smell, and, what is more important, 

 to taste. It appears that one of these species, formerly rare, has 

 lately become very numerous in North America, and is doing great 

 damage to the crops of maize. Mr. Webster suspects that there is a 

 nursery of species of Diahrotica somewhere in Mexico. He has some 

 sensible remarks on their colours and taste, it being believed that 

 the nasty taste (hypothetical, so far as we know, for probably no one 

 has had the courage to chew them, as Professor Plateau did in the 

 case of the currant-moth caterpillar, with the result of finding it 

 not nasty to him) protects the Diahrotica from being eaten by birds, 

 while the colours amount to an exclamation of " we are nasty, and 

 delighted you should know it." We hope Mr. Webster's paper may 

 induce entomologists to make a better acquaintance with the facts 

 about these beetles, so as to ascertain how much truth there may be 

 in the fancies. This seems to be the chief object of his article. He 

 is rather surprised that some of the species appear to be of a more 

 retiring character, and do not advertise their nastiness — hypothetical 

 or real. It is believed that, in South America, some species of the 

 genus Lema have taken advantage of the bad character of the 

 Diabroticas by looking like them, and so getting the benefit of not 

 being eaten, although they are nice (according to hypothesis). Mr. 

 Webster seems somewhat to regret that no North American Lema 

 has yet been clever enough to adopt this hypocritical form of colora- 

 tion. But perhaps there is something in the "environment" in North 

 America adverse to such a line of life. 



Warning Colours and Mimicry. 



In a recent number (1895) of the Journal of the Asiatic Society 

 of Bengal, Mr. Frank Finn, the Deputy Superintendent of the Museum 

 at Calcutta, publishes the first of what he intends to be a series of 

 contributions to a theory of warning colours and mimicry. This 

 excellent first paper is the best kind of " contribution " to a theory, as it 

 consists entirely of experimental observations and not at all of 

 theoretical interpretations. It is the more welcome, as the theory of 

 warning colours has been conspicuous, even among biological theories, 

 for the disproportion between the superstructure and the base of fact. 

 Not long after his arrival in Calcutta, Mr. Finn began a series of 

 experiments as to the palatability of the common warningly-coloured 

 butterflies of the district. For the more agreeable part in the series 

 of dramas he enacted, he cast the common Babbler {Crateropus canonis), 



