222 PRINCIPLES AND CONCLUSIONS. 



was twice driven away, only to return and start digging. Finally, the rock 

 was restored to its original position, and the wasp found the entrance 

 immediately. Clearing away the plants and smoothing the sand about a 

 burrow for a space of 7 or 8 square decimeters sufficed to mislead Bembex 

 entirely, and it was only after a long time spent in digging here and there 

 that the entrance was rediscovered. Bouvier concluded that memory of 

 place and vision play an essential if not exclusive role in the wonderful 

 facility with which Bembex returns to the entrance to its nest. Bouvier 

 has also given an admirable discussion of the faculty of orientation with 

 insects and other articulates (1922:230, 251). 



Marchand (1900:248) found that when a plant growing about 5 cm. 

 from the burrow of Bembex was displaced about the same distance, the 

 insect was unable to relocate the entrance and hunted vainly in all directions 

 for several minutes. The plant was then restored to the original position, 

 and upon its return the wasp flew close to it and soon found the entrance 

 to his nest. 



Memory of place in Osmia. — Ferton (1905:89) has made observations 

 on Osmia rufohirta which indicate that this solitary bee possesses the same 

 remarkable power of memory for place as the social bees and the wasps. 

 After closing its nest in a shell of Helix, an individual of this species moved 

 it to a new position a dozen centimeters away and then went to the plant 

 the leaves of which it was using to make a paste. On its return flights it 

 first flew to position A, slackened its speed without alighting, and then went 

 directly to position B, a path that it followed for a quarter of an hour or 

 more. The observer moved the shell to a new position at C, where the bee 

 found it after some trouble. On leaving, the latter made several vertical 

 flights of orientation above the nest before returning to the plant. On 

 coming back it took the path ABC, though when it went to another plant 

 growing near C, it returned directly to the latter. Soon afterward it 

 carried the shell back to A and again began to work on the original plant. 

 On its return it passed A and, making a slight turn toward B, reached the 

 point C, whence it returned to A, after determining the absence of the nest 

 at C. This experiment, with others that were repeated several times, dem- 

 onstrated that this species is guided by its memory of place. The results 

 obtained with Osmia ferruginea led to the same conclusion, but as this spe- 

 cies does not have the habit of moving its shell, it is less skillful in relocating 

 it and consequently has a poorer memory. 



The manner in which Osmia searches for its nest when displaced indicates 

 that it is guided chiefly by vision. It lands upon all the shells found in its 

 exploration, which would not be the case if it were guided by smell alone. 

 However, the bees of this genus also employ the sense of smell, especially 

 that of contact. Moreover, they can make use of this sense at a distance, 

 as when it is used to guide them to their favorite flowers. It is unnecessary 

 to have recourse to the unlikely hypothesis of an unknown sense, since 

 vision, smell at a distance and in contact, and memory suffice to explain 

 all the observed facts (1906:29). 



Ferton (1908:578) has also discussed Pieron's contention that the homing 

 of Osmia is due to muscular memory and rejects this except for movements 

 repeated a great many times. 



