SOME SILKWORM MOTH REFLEXES. 287 



blackened. A male with antenna? off and eyes unblackened does not 

 find females unless by accident in its aimless moving about, but, if 

 a male with antennre off does come into contact, by chance, with a 

 female, it always (or nearly so) readily and immediately mates. The 

 male is not excited before touching the female, but is immediately and 

 strongly so after coming in contact with her. Males with antennas on 

 become strongly excited when a female is brought within several inches 

 of them. 



The protruded scent-glands of the female are withdrawn into the 

 body immediately on her being touched by a male. If the scent-glands 

 are cut off and put wholly apart from the female, males are as strongly 

 attracted to these isolated scent-glands as they are to unmutilated 

 females ; on the contrary they are not at all attracted to the mutilated 

 females. If the cut-out scent-glands are put by the side of, and but a 

 little apart from, the female from which they are taken, the males 

 always neglect the near-by live female and go directly to the scent- 

 glands. Males attracted to the isolated scent-glands remain by them 

 persistently trying to copulate with them, moving excitedly around 

 and around them and over and over them with the external genitalia 

 vainly trying to seize them. 



The behaviour of males with the antenna of only one side removed 

 is striking. A male with left antenna off, when within three or four 

 inches of a female (with protruded scent-glands), becomes strongly 

 excited and moves energetically around in repeated circles to the right, 

 or rather in a flat spiral thus getting (usually) gradually nearer and 

 nearer the female and finally coming into contact with her, when he 

 is immediately controlled by the contact stimulus. A male with right 

 antenna off circles or spirals to the left. It is a curious sight to see 

 two males with right and left antenna off, respectively, circling violently 

 about in opposite directions when the immobile female a few inches 

 removed protrudes her scent-glands. This behaviour is quite in 

 accordance with Loeb's explanation of the forward movement of 

 bilaterally symmetrical animals. 



The results of all the experiments tried show how rigorously the 

 male moths are controlled b} r the scent attraction (chemotropism) and 

 how absolutely dependent mating (the one adult performance of the 

 males) is on this reaction. If we can find specialized animals in a 

 condition where all attractions and repulsions (stimuli) but one are 

 eliminated we may readily perceive the rigorous control exercised by 

 this remaining one. We are, unfortunately, in the general circum- 

 stances of animal life too much limited to the use of very simply 

 organised animals for reaction and reflex experimentation. This 

 tends to make it difficult to carry over to the behaviour of complexly 

 organized animals the physico-chemical interpretation which is steadily 

 gaining ground as the key to the understanding of the springs and 

 character of the behaviour of the simplest organisms. Bui where the 

 complex stimuli and reactions that determine the behaviour of com- 

 plexly organized forms can lie isolated and studied the inevitableness 

 of much of this behaviour can be recognized. 



Reflexes of Moths without Cephalic and Thoracic Ganglia. — A 

 number of experiments was made to determine the need, or absence 

 of need, of the principal ganglia of the central nervous system in the 

 performance of the two chief reflexes in the silkworm moth's life, viz., 

 mating and egg-laying. 



