76 Bulletin American Museum of Natural History. [Vol. XXII, 



was attacked, but killed 2 of the workers and then ran into the light chamber 

 with a single small larva, which she continued to hold in her mandibles till 

 I retired at 11 o'clock. At 6 a.m. on the following morning I found that she had 

 killed all the workers during the night and had carried about two thirds of 

 the brood into a comer of the dark chamber. At 6.30 a.m. a callow worker 

 had hatched from one of the nude pupae. The female remained with the brood 

 during the day but was very sluggish. July 12, 6.30 a.m. another callow had 

 hatched during the night. The female had left the brood and was clinging to 

 the wet sponge. She seemed to be very weak. At 4 P. m. she was dead. 



In experiments 32 and t,t, the ruhicunda female was interrupted in the 

 display of her instincts by death, caused without doubt by injuries 

 received while killing off the subsericea workers. I believe that such 

 deaths are due to spraying of the distended articular membranes 

 of the limbs with formic acid. Probably at these points the acid 

 is absorbed, and, thus admitted in small quantities into the blood, 

 causes a slow paralysis which, as in the last experiment, overtakes the 

 female in the midst of her catenary reflexes, or instincts. At any rate, 

 in these and most other cases where the females succumb after strug- 

 gling with alien workers, death is certainly not due to wounds or muti- 

 lation. In the following experiments the females, either because of 

 their exceptional strength and agility or the weakness of the subsericea 

 with whom they were confined, survived and were able to display the 

 whole series of their colony -establishing instincts. 



Experiment 34. July 8, 9 a.m. A rubicvinda female was placed in a nest 

 containing t,t, subsericea workers, small and large, 150 cocoons, and a few larvae. 

 The workers at once seized their cocoons and fled into the light chamber. One 

 or two of them attacked the female, but she shook them off and killed one of 

 them. In the meantime some of the workers kept stealing into the dark cham- 

 ber for the purpose of securing cocoons and carried them to the remotest corner 

 of the light chamber. As the morning wore away the female gradually became 

 more and more excited. By i p.m. she had killed five more workers and was 

 busy carrying the cocoons back from the illuminated into the dark chamber, 

 where she had already stored most of them in a corner. In a few minutes she 

 had secured all the cocoons in the light chamber, 36 in number. She inter- 

 rupted this task twice, each time for the purpose of killing a worker that came 

 within her reach. Finally she retired to the dark chamber and began to collect 

 the cocoons into a more compact pile. Two of the workers persisted in stealing 

 in and hurrying back with cocoons taken from the edge of the pile. The female 

 soon perceived this, however, and dispatched both of them. The whole per- 

 formance resem.bled a dulotic expedition in miniature, carried out by a single 

 virgin female instead of by an army of riibicunda workers. In killing the sub- 

 sericea workers, she was quite as ruthless as the workers of her own species 

 but much surer on account of her larger size and greater strength. She ex- 

 hibited very beautifully what may be called the "prancing" movement, so 



