HELIOTROPISM OF ANIMALS 85 



xiv. ADDENDUM: SOME FURTHER EXPERIMENTS ON THE 



GEOTROPISM OF INSECTS 



As I have several times had occasion in this volume to 

 mention the influence of gravity on the orientation of ani- 

 mals a subject which in this form has not yet been discussed 

 in physiological literature it may perhaps be desirable to 

 add a few further facts on animal geotropism. I must say 

 beforehand, however, that my experiments in this field are 

 not yet completed, and that I intend to return to this sub- 

 ject. 



1. I have found that caterpillars (for example, Bombyx 

 neustria) when placed in a hollow vessel creep vertically 

 upward. When we wish to pour such caterpillars out of a 

 vessel, we employ a method opposite to that used in pouring 

 out a liquid ; we must hold the mouth of the vessel upward. 

 When such caterpillars are contained in a glass vessel, the 

 diffuse daylight entering from above in itself would bring 

 about this effect ; I therefore made this experiment in 

 wooden vessels. When the opening of the vessel was 

 directed downward the animals crept upward, and not an 

 animal escaped from the vessel. Geotropism, however, like 

 heliotropism, is especially evident only at certain epochs in 

 the life of the animal ; for the geotropic experiments were 

 not at all times successful even in the same animals. 



2. Small beetles, particularly Coccinella, which can always 

 be procured with ease in great numbers, were placed in a 

 wooden box, and to protect them from the effects of light I 

 put the box in a dark closet. The animals, which were at 

 first scattered over the whole box, were found the next day 

 collected at the highest point in the box, on the upper side, 

 where they remained. When I turned the box about, they 

 changed their orientation and moved again to the top. The 

 behavior of Coccinellidse and other beetles (particularly leaf 



