UNSOLVED PROBLEMS. 151 



or other animals only in degree, the probability being that 

 they are quite different in kind. 



Among the most remarkable results of wholesale migra- 

 tions is wholesale destruction of life in a great variety of 

 ways. In the lemming alone loss of life occurs on the large 

 scale by 



1. Hunger. 



2. Cannibalism. 



3. Falling a prey to feral animals. 



4. Provoking fatal injury by the reindeer. 



5. Drowning 



as well as in other ways ; for it will face fire or other 

 dangers as readily as it does water, and perish rather than 

 avoid, or at least instead of avoiding, peril of whatever cha- 

 racter. Here we have the element of will, deliberation ; so 

 that in one sense the self-immolation of the animals in the 

 sea is to be considered an act of suicide proper. The whole 

 phenomena have a morbid character from the irresistible 

 impulse which urges the lemming armies to set- forth their 

 utter improvidence as to maintenance en route, their inca- 

 pacity to appreciate and avoid dangers, their suicidal im- 

 molation. Possibly these lemming migrations are simply 

 singular illustrations of epidemic morbid impulse, leading to 

 epidemic suicide. 



Wholesale destruction of life, however, is not confined to 

 the migrations of the lemming or other animals. Other 

 illustrations are to be found in the annual or periodical 

 massacre of the neuters by wasps (Westwood), or of the 

 drones by bees (Kirby and Spence). In none of these cases 

 can we explain the object or cause of such dire waste of life. It 

 is easy to assume and to say that a murderous instinct or impulse 

 is developed at certain times or under certain circumstances 

 in the wasp or bee : but this is more a mode of describing the 

 massacre itself, and the fury, unrelentingness, or merciless- 

 ness that characterise it, than an explanation why and how 

 such an impulse should be periodically developed or such a 

 waste of life become necessary or desirable. 



Many animals show a singular prescience of certain classes 



