Tropissns in Insect Behavior, 25 



from it; but the manipulation will have no appreciable 

 effect upon tlie behavior of the insect.* The above be- 

 havior will be true of practically any species of surface- 

 feeding caterpillar provided the larva has not just 

 hatched from the egg or just emerged from hibernating, 

 or is about to pupate or to hibernate. If a horizontal 

 maze is substituted for the vertical one the behavior will 

 be essentially the same. Since these caterpillars cross 

 the rays of light, the wind and the vertical line at every 

 possible angle, the behavior is neither a phototropism 

 nor an anaemotropism nor a geotropism. 



Secure a piece of glass tubing large enough to allow 

 free movements but too narrow to permit the larva to 

 turn around in it. By such a device it is possible to in- 

 troduce the caterpillar to the maze with its head pointing 

 in any desired direction. Under such conditions the 

 caterpillar, when introduced to the maze, always starts 

 off in the direction in which its head happens to be turned 

 at the time. Irrespective of the direction of either the 

 light or of the wind or of the pull of gravitation, it con- 

 tinues in that direction until some new stimulus is 

 reached. There is no automatic adjusting of the body so 

 as to have symmetrical portions equally stimulated. Evi- 

 dently, except perhaps just after emerging from the egg 

 or a state of hibernation, or immediately before pupating 

 or hibernating, there is nothing about the behavior of 

 surface-feeding caterpillars to warrant the assumption 

 that these locomotions are tropisms. The movements 

 made in locomotion are identical with those executed by 

 animals that learn by the trial and error method. In- 

 stinctively the caterpillars are physiologically attuned to 

 a certain environment. Outside that environment there 



* Turner, G. H.; The Locomotions of Surface-Feeding Caterpillars 

 are not Tropisms. Biological Bulletin, Vol. XXXIV, 1918, pp. 137-148. 



