We know now that flying insects, once in sight of the spot where their nest is established, find the orifice of the latter by means of visual sensations fixed in their memory. It now remains to know the manner in which they have been led to the point where this spot becomes perceptible.
Bethe enclosed some bees in a box, and set them at liberty at least three or four kilometers from their hive. All returned to the domicile except two, which flew to the box placed upon a stone. It is an "unknown force" which guided them, says Bethe, but Buttel-Reepen and Forel observe that the bees had foraged over a wide range, that they recognized guiding points, and that the two which remained in the box were young ones which had not yet gone a-f oraging. Fabre carried some Cha-licodomas far from their masonry nest, and liberated them at distances which varied from one to two kilometers. Of the 144 individuals, 47 returned to the nest after intervals of from five minutes to several hours, and Fabre concluded that these bees are guided by a special sense of orientation. It is very clear, however, that some insects erred ; that the greater number were lost, and that the others, more lu»cky, had noticed guiding points. I have made a calculation, in fact, that the number of bees which returned to the nest is reduced in proportion as the distance is increased : at two kilometers, five out of ten; at three kilometers, from three to four ; and at four kilometers a little less than two. The influence of the memory of places is plain.
To avoid criticism, Bethe and Fabre carried their insects to places which they had never visited. The hives of the former were situated not far from Strasburg. The bees were liberated in the city itself, at 350, 400, and 650 meters from the hives, to which they returned after a time which varied from one minute and a half to ten and a half minutes. The insects of the second were mining-wasps of the genus Cerceris, which, liberated in the middle of the city of Carpentras at three kilometers from their nests, returned there in the proportion of five out of ten. But it is very certain that bees frequent cities, where they know marvelously well how to discover sweet things, and the long time which they took to return shows that they knew the streets of Strasburg, for they fly at five-hundred meters a minute in the open country. As to Fabre rs Cerceris, perhaps they did not know Carpentras, but they knew the neighborhood, where some of them reached known places which guided them to their nests.
Set at liberty in a place which they have never reached in the course of their journeys, insects seek vainly for their route. Buttel-Reepen carried a closed hive seven kilometers and took from it some bees, which he kept in a box and set free forty and eighty meters from the new place. They did not know how to return to the place where their nest had been, and Bethe explained this: phenomenon by saying that the "unknown force" acts only from three to four kilometers. But this is a mistake, for they did not return to the displaced hive however near it was. Is it necessary further to establish the fact that the memory of places is confused with the "unknown force" of Bethe and the "topographic feeling" of Fabre? Romanes established a hive in the second story of a house which was separated from the sea by a lawn and which had at the right and at the left beds of flowers. When the bees had formed the habit of entering and going out by the window of the apartment, Romanes took advantage of their nocturnal sleep by closing the door of the hive, and next day captured a certain number which he used in his experiments. Some were liberated at sea not far from the coast, others upon the shore two hundred yards from the house, others in the flower beds. The last all returned to the hive ; but none of the others returned, because they had not explored the lawn and the sea. Yung made a similar experiment on Lake Geneva, and concludes with Romanes that bees are incapable of reaching a point which is known but not perceptible when they have not explored the region which separates them from it.
To the memory of visual sensations must be added the memory of olfactory sensations. Ferton gives some curious examples in his studies of the shell-inhabiting Osmias. Displaced for some centimeters, the shell in which the bee nests is found on the sand even when it is crushed; it is also found when it is hidden in a tuft of herbage ; and when it is replaced by another shell of the same species the insect notices the fact, disdains the substitute, and leaves in search of the shell which belongs to it.