568 THE SENSES AND SENSORY ORGANS. 



and then took a new departure, only to run against a second 

 obstacle. From this he concludes that they do not see the 



/ 



obstacles. It might have occurred to Plateau that such insects 

 live either on the ground or amongst shrubs, branches, grass, 

 etc. It is their habit to climb over obstacles and not to 

 go round them; it is, perhaps, an error of judgment when a 

 Beetle or Grasshopper runs at a vertical wall of cardboard, 

 but such vertical walls are a new experience to the insect. 

 Again, it is at the edges of stones that many predatory insects 

 find their prey ; they run round them, and not over them, 

 examining the edge ; why should not an insect mistake a card 

 for a stone, and, finding it an unwonted object, start to examine 

 the next obstacle ? Such experiments prove nothing. 



Bees appear to avoid obstacles of this kind better than most 

 insects, but their nests are labyrinths. 



3. Observations made in the open air, in which he thinks 

 that insects evince a want of clear vision. He cites a Dragon- 

 fly which, after having been disturbed, made a long iiight and 

 frequently realighted upon exactly the same spot, as Dragon- 

 flies will. He thinks this insect could not see his net, because 

 he succeeded in capturing it by keeping the net still, and 

 argues that the insect sees ill ; but how does he explain its 

 periodic return to the exact spot it had left ? if it could not see 

 the net, how could it see the twig on which it was accustomed 

 to rest ? How can the mazy dances of insects be explained ? 

 How is it the Lepidoptera do not tear themselves on projecting 

 brambles in their flight if they cannot see them? Why does 

 Volucella resemble a hyrnenopterous insect ? Why are the 

 Syrphidse like Wasps? Every entomologist whose judgment 

 is not warped by a desire to verify M tiller's theory of vision 

 will recall a thousand instances in which he has been impressed 

 with the belief that insects see most acutely. 



Plateau forgets in many cases the strong influence of curiosity 

 amongst animals; who has not observed the manner in which 

 animals and even insects investigate unknown objects? When 

 he tells us that a Syrphus hovered in front of his finger, with 

 which he had pushed away the flower before which the insect 



