Carpenter, Reactions of Drosophila. 487 



by another and more complicated one. The latter belongs in 

 that category of reactions included under the somewhat vague 

 designation of "pleasure-pain" behavior, (For a discussion, see 

 Jennings '04, pp. 248-249, and '06, pp. 332, 340.) Of reactions 

 of this kind Jennings and others have pointed out abundant 

 examples among the lower organisms. Holmes ('05) has described 

 in Ranatra, after one eye had been bhnded, conduct nearly 

 similar to that observed in Drosophila. He concludes that the 

 "phototaxis" of Ranatra seems in many ways to be "intermediate 

 between purely reflex conduct on the one hand, and conduct of 

 the pleasure-pain type on the other." This conclusion applies 

 equally well to Drosophila. 



The production of convulsive reflexes. — In the experiments with 

 an increased temperature, as above described, it sometimes hap- 

 pened that an insect, instead of creeping along the floor or roof of 

 the box, would fly or hop toward the light. If it were under con- 

 siderable headway it might, in spite of its negative thermotropism, 

 be carried by its momentum into the immersed portion of the box. 

 This rapid form of locomotion could often be induced by tapping 

 on the exposed end of the box. A fly thus carried into a tempera- 

 ture of 45° C. soon became violently active. The high tempera- 

 ture evidently acted as a powerful kinetic stimulus, so that nervous 

 impulses overflowed, as it were, from the sensory nerves concerned 

 with temperature into the entire motor nervous system, producing 

 a convulsive reflex. The wings vibrated with great rapidity, and 

 the legs, abdomen, head and mouth-parts were afi^ected by spas- 

 modic contractions of their muscles. These activities often 

 resulted in a peculiar spinning motion, and carried the fly rapidly 

 about from place to place. Owing to the incHnation of the box 

 the insects usually tended toward the lower or immersed end, 

 where they shortly succumbed to the heat, often dying in a charac- 

 teristic attitude, with wings rigidly extended. Occasionally, how- 

 ever, the energetic, haphazard motor reflexes carried a fly out of 

 the heated area into the cool, elevated region of the box, where its 

 convulsive movements ceased, and it shortly began to creep about, 

 restored, apparently, to its former condition. 



When the experiments with reduced temperature were being 

 performed, flies were introduced into the cold portion of the box. 

 Many of these also gave the convulsive reflex before settling down 

 into the quiet, benumbed condition eventually brought on by the 



