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 flight 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 hymenopterous insect? Why are the 
Syrphide like Wasps? Every entomologist whose judgment 
is not warped by a desire to verify Miiller’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 
