53 2 ANTS. 



squished in ants: fir>t, random behavior, like that observed by Jennings, 

 Holmes, Yerke> and others in so many of the lower invertebrates and 

 by Lloyd Morgan, Thorndike. Hobhouse and others in the higher 

 animals. Random, or " trial and error " movements, occur, so to speak, 

 in the very bosom of the instincts, as, for example, when an ant goes 

 out to forage for food that has not as yet been located. She moves 

 along slowly and in a very irregular course, palpating all the elevations 

 and depressions in her path, till she happens on some bit of food. Then 

 her demeanor suddenly changes, she seizes the food and returns with 

 it rapidly to the nest. Of course, there are also random movements 

 of a more primitive type, such as the righting movements, or those per- 

 formed by an ant that is trying to extricate herself from some sticky 

 substance, from the jaws of another ant, or from under a pebble or 

 bit of earth that has fallen on her body. Such movements have the 

 same teleological significance which they have in other animals : they 

 greatly increase the likelihood of escape and survival, and through what 

 Jennings calls the " readier resolution of physiological states after 

 repetition " they have a prospective value in relation to future circum- 

 stances of a similar character. 



A second type of behavior is that in which the organism when con- 

 fronted with a new situation does not proceed to make random move- 

 ments, but at once adapts itself to. the situation by a process which some 

 authors (Loeb, Turner) have called associative memory. The nature 

 of this process is, of course, a matter of conjecture and on this account 

 it is differently conceived by different authors. Before considering 

 this matter, however, we may pass in review the main facts that compel 

 us to postulate the existence of some form of memory in ants. These 

 facts may be grouped under the heads of foraging and homing, recog- 

 nition of nest mates and aliens, communication, imitation, cooperation 

 and docility. 



i. Foraging and Homing. Forel was the first to show that ants 

 are guided in their foraging and homing excursions very largely by 

 their sense of contact-odor, i. c., that they recognize by means of their 

 antennal sense-organs the odor-form, and hence also the direction of 

 the trails laid down by their own feet and those of their nest mates. 

 He showed also that some blind or small-eyed ants, like the Dorylines 

 and Lasins, ants which habitually forage in files, stick very close to 

 their odoriferous trails and therefore rely mainly or altogether on their 

 topochemical sense in finding their way back to the nest, whereas 

 others, like the species of Formica, use their eyes as well, and there- 

 fore often abandon the sinuosities of the trail and make straight for 

 their feeding grounds or for the nest. These observations have been 



