This observation by the clever entomologist seems surely to show that sight and a memory of places play a large part in the orientation of flying insects. We know, moreover, that these insects are incapable of directing themselves when their eyes are covered with opaque varnish, and Buttel-Reepen observes that bees, when twilight comes, fall to the ground instead of reentering the nest.

The same biologist adds that some bees lose forever their memory of places and have to begin a new apprenticeship after they have been given certain narcotics (ether, chloroform, etc.) ; that they undergo a progressive enfeebling of the memory under the influence of cold, of baths, and after five or six weeks the memory of the place of the nest is lost. Finally, their memory of places is less tenacious in summer than in winter, because "new impressions come to replace the old ones." This last fact is corroborated by the observations of François Huber and of Lovell, who saw bees return to a window where the preceding autumn they had found honey (see page 116), associating the memory of an especial place with the gustatory sensations which they had experienced at that spot. But a psychic process such as this cannot take place without observation, and observation, because of too great a similarity, may be at fault in the visual sensations. Forel says:

"A bumblebees' nest which I had put on a window ledge, showed me what trouble the bumblebees which returned from their excursions had in distinguishing this window from other windows in the same façade. The first few times especially, they flew a long time around the other windows before finding the right one."

Lubbock with the -wasps and Buttel-Reepen with the bees have recorded errors of this kind.

These facts have already cleared up a question which we <are considering, but before concluding it is necessary to follow the problem a little further and study the return to a known place with or without indicating points.