Habits, etc., of the " IValking-Stick" [Aplopus iiiayeri). 53 



of which were now at rest, although they were caged nearb)- so as to expe- 

 rience the same Hght conditions. At 6 o'clock four of the blind ones were 

 still active, although the sun had been shining for half an hour. At 8 o'clock 

 all were at rest, yet they were more than an hour later than the control in 

 responding to the morning light. When these blind insects had been at rest 

 for 2 hours they were placed in the dark-room, where all became active after 

 about an hour. They were then brought into the light and assumed the 

 attitude of rest within 12 minutes. 



In the evening the ones with painted eyes became active 30 to 45 

 minutes earlier than the normal ones did. At 6'' 12" p. m. not one of 50 

 normal insects had moved, while 5 of the 8 blind ones had been moving 

 actively for 40 minutes. Aplopi probably appreciate light to some extent 

 through their bodies, but more acutely by means of their eyes ; thus night 

 appears to come earlier and day later to the blind ones. The 2 blind males 

 failed to pair with either of the 6 blind females, though normal males and 

 females usually mated when they were caged together. 



Blind and normal females were observed in their natural environment 

 on Siiriaiia bushes. Here the blind individuals also became active earlier in 

 the evening than the normal ones. 



When the strong light of a bull's-eye lantern is thrown on a normal one 

 of these insects at night, it turns its head from side to side and gives evi- 

 dence of seeing the light. 



These experiments seem to show that Aplopus may respond to light 

 and darkness through its general body surfaces, but that it does so much less 

 readily, or slower, than by means of its optic organs. 



EXPERIMENTS WITH LIGHT RAYS OF DIFFERENT LENGTHS. 



It became desirable at this stage to know whether the insects responded 

 to white light as a complex whole or to some of its constituent rays. Several 

 experiments were conducted in the attempt to solve this problem. 



Light was passed through a vessel containing carbon bisulphide, which 

 serves to eliminate the ultra-violet rays. This is the well-known e.xperi- 

 ment first performed by Sir John Lubbock on ants. A dark-jar was ar- 

 ranged and two of the " walking-sticks " were placed in it. After thev had 

 been quiet for 10 minutes the jar was covered by a vessel containing sea- 

 water in order to test the effect of the subdued light which was transmitted 

 by the liquid. The animals under this condition remained motionless for 

 25 minutes. The vessel containing the sea-water was then removed, and the 

 jar allowed to stand uncovered for 10 minutes. The insects still retained 

 their daylight state of rest. A vessel containing carbon bisulphide was now 

 placed over the jar, thus admitting daylight minus its ultra-violet rays. The 

 Aplopi remained perfectly motionless in this light for 85 minutes and were 

 then removed from the jar. It thus seems apparent that this insect is not 



