278 MENTAL EVOLUTION IN ANIMALS. 



to have it removed ; therefore probably they do not excrete 

 solely for the good of the ants."* 



Coming now to the other branch of the subject, after due 

 reflection I can only think of two or three instincts which 

 could possibly be cited as presenting the appearance of being 

 detrimental to the species which manifest them. I shall 

 therefore consider these cases separately. 



1. Suicide of Scorpion. — The state of the evidence on this 

 subject will be found in my other work.f It will there be 

 seen that two or three independent witnesses — including a 

 friend of Dr. Allen Thomson on whose accuracy he says he 

 can rely — bear testimony to the truth of the popular saying 

 that when a scorpion is surrounded by fire, or otherwise 

 exposed to undue heat, it will commit suicide by stinging 

 itself to death. It will be seen, however, by referring to the 

 correspondence in question, that the alleged facts are disputed 

 by other observers, and also, as I have already indicated, that 

 they were not observed by Dr. Thomson himself. 



The effect of republishing this correspondence and of 

 pointing out the desirability of obtaining further evidence 

 upon the matter, has been to induce two very competent 

 naturalists to make some observations upon the subject. One 

 of these naturalists is Professor Lankester, who published his 

 observations in the " Journal of the Linnean Society " (1882), 

 and the other is Professor Lloyd Morgan, who published his 

 results in " Nature " (vol. xxvii, p. 313). Both these observers 

 agree that the scorpions never commit suicide, and as Mr. 

 Morgan exposed the animals to a variety of dreadful tortures 

 with a uniformly negative result, I think the question may 

 now be considered as closed. Moreover Mr. G. Bidie, who 

 started the previous correspondence in "Nature," has recently 

 addressed another letter to that Journal^ in which he makes 

 the not improbable suggestion that, as in his experiments he 

 applied heat by condensing the rays of the sun with a lens 

 upon a small point of the scorpion's back, the animal in 

 stinging itself " may have merely been trying to get rid of an 

 imaginary enemy." 



2. Insects flying through Flame. — The determination shown 

 by many kinds of insects to fly towards and through a flame 

 is unquestionably due to instinct, and as such might be ad- 



* Origin of Species, p. 208. + Animal Intelligence, pp. 222-5. 



% July 12, ]SS;J. 



