640 Reflexes, Instincts, and Intelligence 



the ones covered turned down; the ones below stood undecided; I cropped 

 the jacket completely; the mass began issuing from the exit again; I pulled 

 off the jacket, and again the whole community of excited bees flowed that 

 is the word for it, so perfectly aligned and so evenly moving were all the 

 individuals of the bee current up to the closed top of the hive. Leaving 

 the jacket off permanently, I prevented the issuing of the swarm until the 

 ecstasy was passed and the usual quietly busy life of the hive was resumed. 

 About three hours later there was a similar performance and failure to issue 

 from the quickly unjacketed hive. On the next day another attempt to 

 swarm was made, and after nearly an hour of struggling and moving up 

 and down, depending on my manipulation of the black jacket, most of the 

 bees got out of the hive's opening and the swarming came off on a weed 

 bunch near the laboratory. That the issuance from the hive at swarming 

 time depends upon a sudden extra-development of positive heliotropism 

 seems obvious. The ecstasy comes and the bees crowd for the one spot of 

 light in the normal hive, namely, the entrance opening. But when the cover- 

 ing jacket is lifted and the light comes strongly in from above my hive was 

 under a skylight they rush toward the top, that is, toward the light. Jacket 

 on and light shut off from above, down they rush; jacket off and light 

 stronger from above than below and they respond like iron filings in front 

 of an electromagnet which has its current suddenly turned on. What pro- 

 duces the sudden strong heliotropism just as the swarming ecstasy comes 

 on ? That is beyond my observation. 



The other example is as follows: Silkworm moths (Bombyx mori) are 

 sexually mature and eager to mate immediately on issuing from the pupal 

 cocoon. They take no food (their mouth-parts are atrophied), they do not 

 fly, they are unresponsive to light; their whole behavior, in fact, is deter- 

 mined by their response to the mating and egg-laying instincts. We have 

 thus an animal of considerable complexity of organization, belonging to a 

 group of organisms well advanced in the animal scale, in a most simple 

 state for experimentation. 



The female moth, nearly immobile, protrudes a paired scent-organ from 

 the hindmost abdominal segment, and the male, walking nervously about 

 and fluttering its useless wings, soon finds the female by virtue of its chemo- 

 tactic response to the emanating odor. Males find the females exclusively 

 by this response. 



A male with antennae intact, but with eyes blackened, finds females im- 

 mediately and with just as much precision as those with eyes unblackened. 

 A male with antennae off and eyes unblackened does not find females unless 

 by accident in its aimless moving about. But if a male with antennae 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 



