1578 THE STORY OF THE UNIVERSE 



beetles alight abruptly, though voluntarily, they as- 

 sume that appearance of death which lasts for a few 

 moments. Some species, indeed, are so highly sen- 

 sitive that the slightest touch, or even a sudden men- 

 ace, will instantly throw them into this motionless, 

 death-simulating condition. Curiously enough, the 

 same causes which produce this trance in slow-mov- 

 ing species, like those of Scarabaeus, for example, 

 have a precisely contrary effect on species endowed 

 with great activity. Rapacious beetles, when dis- 

 turbed, scuttle quickly out of sight, and some water- 

 beetles spin about the surface, in circles or zigzag 

 lines, so rapidly as to confuse the eye. The common 

 long-legged spiders (Pholcus) when approached 

 draw their feet together in the middle of the web, 

 and spin the body round with such velocity as to re- 

 semble a whirligig. 



Certain mammals and birds also possess the death- 

 simulating instinct, though it is hardly possible to 

 believe that the action springs from the same imme- 

 diate cause in vertebrates and in insects. In the lat- 

 ter, it appears to be a purely physical instinct, the 

 direct result of an extraneous cause, and resembling 

 the motions of a plant. In mammals and birds, it is 

 evident that violent emotion, and not the rough 

 handling experienced, is the final cause of the swoon. 



Passing over venomous snakes, skunks, and a few 

 other species in which the presence of danger ex- 

 cites only anger, fear has a powerful, and in some 

 cases a disabling, effect on animals; and it is this 

 paralyzing effect of fear on which the death-feign- 

 ing instinct, found only in a few widely separated 



