HOMING FACULTY. 221 



22 flew through the window away from the nest, 16 through the one toward 

 it; the majority returned in the first 15 minutes, but they continued to 

 arrive for another quarter of an hour. 



The experiments all served to show that the two species of wasps em- 

 ployed have no sense of direction in the form of a mysterious second sense 

 or of an ability to keep track of the turns and changes in a journey. In 

 spite of the fact that the wire cage permitted the use of sight, they fre- 

 quently started in a wrong direction as they flew out. In many instances, 

 however, these wasps returned to the nest and it seems probable that they 

 did this by rising higher and higher in the air and discovering some objects 

 that served them as landmarks. 



Disturbance of memory in wasps. — In their study of the homing in 

 solitary wasps (1898:367), the Peckhams concluded that if these had an 

 innate sense of direction they would not need to make a study of the sur- 

 roundings of the nest in order to find the way back, but in the absence of 

 such a sense common prudence would require the careful inspection of the 

 location before the outward flight. After days spent in flying about the 

 garden, it would seem that further study of the precise locality might be 

 superfluous, but the wasps did not find it so. They made repeated and 

 detailed studies of the surroundings of the nests, and when their prey was 

 laid down for a moment on the return, they noted the place carefully before 

 leaving it. If the scrutiny of the objects about the nest makes no impres- 

 sion on the wasp, she should not be bothered or misled when weeds and 

 stones are removed and the ground smoothed, but this is just what happens. 

 Aporus fasciatus lost her way entirely when a leaf that covered the nest 

 was broken off, but found it readily when this was replaced. All the species 

 of Cerceris were extremely annoyed by new objects placed near the nests, 

 and Ammophila refused to make use of her burrow after deep lines were 

 drawn in the dust before it. The same annoyance was exhibited when 

 any change whatever was made near the spot where the prey was placed, 

 and experience showed how important it was not to disarrange the grass 

 or other plants on such occasions. Marchal (1900:1113) has given an 

 account of the errors made by Pompilus in the return to the nest and reaches 

 a similar conclusion to the effect that it is not guided by a special sense 

 of direction, but solely by vision and memory. 



Observations on the homing of Bembex and Pompilus. — Stimu- 

 lated by the observations of Fabre on Bembex (1879:261), which led to the 

 conclusion that neither memory of place, sight, nor smell guided the insect, 

 Bouvier (1900:874) investigated the behavior of Bembex labiatus. His 

 first results were in agreement with those of Fabre to the effect that the 

 wasp always returned close to the entrance of its nest, regardless of the 

 substances used to mask this. However, when the objects have a consider- 

 able size, the insect is completely lost and sometimes spends hours seeking 

 here and there before relocating its burrow. When the latter was covered 

 with a flat stone about a decimeter in size, the wasp lighted on the stone, 

 scratched it, hunted beneath it, and found the entrance only after much 

 effort. The next day the stone was displaced about 2 dm. from the new 

 entrance that had been made, with the result that the insect flew at once 

 to the edge of the stone and began to dig as though at the right place. • He 



