Carpenter, Reactions of Drosophila. 489 



temperature in ordinary daylight. Ten insects were placed in a 

 water-tight glass vessel with thin walls, and the latter was immersed 

 in water which had previously been heated to 30° C. The con- 

 vulsive reflexes did not appear. The temperature was then 

 gradually raised. The flies showed the first convulsive reflexes 

 between 36° and 38°, and these became general between 38° and 

 40°. The experiment was twice repeated with the same results. 

 It follows, then, that the hght of a 480 candlepower electric arc, 

 at a distance of from 2 to 3 cm., calls forth the convulsive reflex 

 at a temperature at which, in ordinary dayhght, this reaction does 

 not occur. 



In view of the above-described effects of excessive temperature 

 and light stimulation, it seemed probable that certain volatile 

 substances, acting through the end-organs and nerves concerned 

 with chemical sense, might also prove sufficiently stimulating for 

 the production of convulsive reflexes. The following experiment 

 was, therefore, made. The floor of the glass box used in the 

 temperature experiments was moistened near one end along a 

 line drawn from side to side, first with aqua ammonia, and after- 

 ward with glacial acetic acid. This end of the box was in each 

 instance turned toward a window, and the flies, at first assembled 

 at the other end, crept in the direction of the hght. There was 

 little or no evidence of a negative tropic reaction. But when the 

 insects came close to either fluid the irritating vapors produced 

 violent convulsive reflexes. Some of the insects were whirled into 

 the fluid where they perished; others were carried to a distance 

 and soon recovered. One fly spun about for fifteen seconds dur- 

 ing a convulsive reflex induced by acetic acid, and finally reached 

 a position outside the stimulating area. Its excessive activity 

 then ceased, and it was soon creeping about in the usual 

 way. 



The student of animal behavior will ask himself how this con- 

 vulsive reflex is related to other reactions of animals. It deserves 

 this consideration since it is, in Drosophila, a normal reaction. 

 The conditions necessary to call it forth are, it is true, extreme, 

 and usually cause the death of the fly if allowed to continue. The 

 reflex, however, is not a death struggle due to pathological changes 

 in the body. If it removes the insect from the stimulating region 

 the excessive activity gives way to ordinary movements, and the 

 insect appears to be none the worse for its experience. 



