486 JOURNAL OF ECONOMIC ENTOMOLOGY [Vol. 5 



in determining this, since the stronger light is to be found towards the 

 tips of the branches. 



Geotaxis. When placed on a thin cork board, in a vertical position, 

 the young scale insects began climbing upward against the direction of 

 gravity. This did not continue in all cases until the form had reached 

 the top of the board, but many of the specimens seemed to stop when 

 they reached a height of six or eight inches, though several continued 

 to the top of the board, twelve inches in height. This method of 

 reaction, crawling upward, or negative geotaxis, affords us another 

 factor in the assistance of the light in aiding the young scale insects to 

 reach the newer portions of the growth of the branch, since this part 

 usually projects upward. 



Chemotaxis. A very small amount of strong hydrochloric acid, 

 nitric acid, and 95 per cent alcohol were placed in the midst of a large 

 number of young scales on a glass slide, and their movements observed 

 under a binocular. To each of these substances all of the young 

 scales showed a very marked negatively chemotactic response. It 

 would be interesting to test out the effect of a weak tannic acid solu- 

 tion in this relation, ,and also an extract of the juices of the twigs of the 

 oak, where we would expect a positive reaction; but though this was 

 the intention of the writer, the matter was overlooked until all of the 

 young scales had become old enough to have fixed themselves in their 

 places on the tree. 



Thigmotaxis. The young scale insects show very strongly positive 

 thigmotactic propensities. A young nymph which had become turned 

 on its dorsal surface was observed to juggle an unhatched egg, much 

 as a clown would a ball, moving it about with its legs from nine o'clock 

 one morning until five o'clock that afternoon. Observations were 

 discontinued at that time for the day; but the next morning, the per- 

 formance was still in progress, and continued until about two o'clock 

 that afternoon. At that time the young scale emerged from the egg 

 and it was only with difficulty that the newly emerged individual could 

 escape from the grasp of its young foster-parent. All of this misspent 

 energy came from the attempt of the form to '' right " itself, and hav- 

 ing caught hold of the egg in its efforts to do this, it lacked sufficient 

 organization of its nervous system to profit from an experience of this 

 kind and continued its futile efforts in this direction until the hatching 

 of the egg relieved it of the object of its misdirected energies. When 

 placed upon their dorsal surfaces they grasp very quickly and cling 

 tightly to such objects held out to them as the fibres of a camel's hair 

 brush, small straws, etc. This positive thigmotaxis is, of course, highly 

 adaptive in nature, and serves to keep the animal in contact with the 

 twig on which it has hatched and will continue to spend its further 

 existence. 



