966 The American Naturalist. [November,. 
PSYCHOLOGY. 
Subjective Defense in the Lower Animals.—In this paper 
I use the word “ defense" in its broadest sense, not only as the ante- 
thesis of offence, but in the sense of protection. The instinct of de- 
fense or self protection is greatly developed in the lower animals, so 
much so,that the observant naturalist finds evidence of it even in 
microscopic organisms. 
On one occasion I opened the burrow of an itch insect (Acarus), and 
allowed the serum to float out the little parasite which dwelt therein. 
I could, with the assistance of a good French lens (X 15 diameters) 
closely see it moving along on the surface of the skin. I touched it 
with the point of a needle, and at once it stopped all motion and 
feigned death. In a few moments the little animal regained its feet. 
and slowly moved off, only to again feign death as soon I touched it with 
the needle. This habit of letusimulation (letum, death, and simulare, 
to feign), I have noticed in much lower animals, and am convinced 
that they make use of this strategy for the purpose of self-protection. 
A minute fresh water animacule (rhizopod) retracts its hair-like feet, 
feigns death and sinks, whenever its enemy, a water louse, approaches 
it. I have witnessed this occurrence on several occasions, and have, 
likewise, seen Rhizopoda return to their feeding-grounds as soon as their 
enemy has disappeared. A fresh-water worm practices letusimulation 
when approached by the giant water-beetle, and many of the micro- 
scopic infusory animalcules likewise make use of the same sagacious 
subterfuge when surprised by their enemies. Death-feigning is prac- 
ticed by most of the slow-moving beetles, especially is this noticeable 
in the tumble-bug and bombardier-beetle. "This last-mentioned insect, 
notwithstanding its disgusting odor, is the favorite food of some of the 
birds, noticeably, the jay and the cardinal. They will not touch it if 
killed and offered to them; numerous experiments have taught me that 
these birds regard it as unsuitable food unless taken alive. There is, 
probably, some post-mortem change in the juices of the beetle, which 
renders it unpalatable. The object of letusimulation in this beetle is 
made perfectly obvious. In a paper on “Animal Letusimulants," pub- 
lished in the March number of Atlantic Monthly, I account for the 
origin of death-feigning in animals, as follows: ‘ Most animals are 
slain for food by other animals; there is a continual struggle for exist- 
ence. Most of the carnivora and insectivora prefer freshly killed food 
pere TT D 
