The animal in question was the itch mite (_Sarcoptes hominis_), which is frequently met with by physicians in practice, but which is rarely seen, although it is very often felt, by mankind, especially by those unfortunates who are forced by circumstances to dwell amid squalid and filthy surroundings. _Sarcoptes hominis_ is eminently a creature of filth, and is primarily a scavenger living on the dead and cast-off products of the skin. It is only when the desire for perpetuating its race seizes it that it burrows into the skin, thereby producing the intolerable itching which has given to it its very appropriate name. It is only the females that make tunnels in the skin; the males move freely over the surface of the epidermis. The females make tunnels or _cuniculi_ in the cuticle, in which they lay their eggs, and they can readily be removed from these burrows with a needle. While observing one of these minute _acarii_ through a pocket lens, as it crawled slowly on the surface of the skin, I wished to examine the under surface of its body. When I touched it with the point of a needle in attempting to turn it upon its back, it at once ceased to crawl and drew in its short, turtle-like legs toward its sides. It remained absolutely without motion for several seconds, and then slowly resumed its march. Again I touched it, and again it came to a halt, and took up its onward march only after several seconds had elapsed. Again and again I performed this experiment with like results; finally, the little traveller became thoroughly chilled, and, after a fruitless endeavor to again penetrate the skin, ceased all motion and died. Many of the coleoptera are good letisimulants. The common tumble-bug (_Canthon lævis_), which may be seen any day in August rolling its ball of manure, in which are its eggs, to some suitable place of interment, is a remarkable death-feigner. Touch it, and at once it falls over, apparently dead. It draws in its legs, which become stiff and rigid; even its antennæ are motionless. You may pick it up and examine it closely; it will not give the slightest sign of life. Place it on the ground and retire a little from it, and, in a few moments, you will see it erect one of its antennæ and then the other. Its ears are in its antennæ, and it is listening for dangerous sounds. Move your foot or stamp upon the ground, and back they go, and the beetle again becomes seemingly moribund. This you may do several times, but the little animal, soon discovering that the sounds you make are not indicative of peril to it, scrambles to its feet and resumes the rolling of its precious ball. The habit of making use of this subterfuge is undoubtedly instinctive in this creature; but the line of action governing the use of the stratagem is evidently suggested by intelligent, correlated ideation.