58 Papers from the Marine Biological Laboratory at Tortugas. 



A point of some interest is that Aplopus seems to prefer the female to 

 occupy a horizontal position in mating. During the first experiment with 

 the " stick-female " it was placed in a vertical position and caged with males 

 in the dark for two days without a result. In the experiment above the 

 "stick-female" was first placed vertically and remained so for 1.5 hours 

 without attracting a male. When it was changed to a horizontal position a 

 male paired with it in less than an hour. All of the normal pairs observed 

 were in a more or less horizontal position. It may be that the attitudes of 

 the male are difficult to assume unless the female stands horizontally. 



The cage with the " stick-female " and four males was again returned 

 to the dark-room and after 2.5 hours a second male was found standing on 

 the decoy. He remained in this position for over 3 hours, which was a much 

 longer time than I had known a male to stand over a normal female without 

 copulating with her. After this time, however, he began the usual mating 

 movements and copulated perfectly with the abdomen. This was, then, the 

 second time that the amputated abdomen of the female had been paired with, 

 and each time by a different male. No doubt, therefore, remains that the 

 male Aplopus may pair normally with the female without any " communica- 

 tion." " courtship," or psychical processes having taken place between them. 



SUMMARY AND CONCLUSIONS. 



1. The habits of Aplopus inayeri on its food-plant Suriana maritima are 

 as truly protectively adapted as is its singular stick-like appearance. The 

 large females in their color and shape resemble the stem of this plant ; the 

 males are greenish and well concealed among the leafed twigs, while the 

 eggs are peculiarly similar to the seeds of Suriana in size and color, although 

 differing in shape. The insect is nocturnal and only occasionally moves in 

 the daylight ; then as a rule with a slow, waving motion suggesting the move- 

 ment of a branch swinging in a light breeze. To escape enemies it may fall 

 bodily from its position and become lost among the lower branches of the 

 shrub, or at times it may fall entirely to the ground, where it will lie motion- 

 less for several minutes as if feigning death. 



2. Aplopus becomes active by a much brighter light in the evening than 

 that by which it comes to rest in the morning. Both reactions are, how- 

 ever, responses to light and not to a physiological periodicity, as may be 

 shown with dark-room experiments. If these insects are blinded by paint- 

 ing their eyes with lampblack paste, they still respond to light and darkness, 

 although much slower than normally. 



3. They gave no response to sunlight lacking the ultra-violet rays, and 

 were equally indifferent to red and blue lights, acting in all as though they 

 were in ordinary daylight. 



4. Aplopus gives no indication of hearing sounds of various intensities. 



5. These insects during the day, while inactive, may be made to assume 



