Ddpino on Fcauidation 183 



Delpino in 1865 and 1866, are stated by him to furnish a constant 

 confirmation of the laws pointed out by Sprengel. 



One part of his hypothesis from which we wholly dissent, and 

 which his observations seem to us never to touch at all, is that the 

 vivid colours of flowers have the effect of attracting insects to 

 them. As we have already said in a preceding paper in this num- 

 ber of the Journal, insects are short-sighted animals. However 

 strong their other senses may be, and however powerful their sight 

 may be close at hand, (a point as to which we know nothing), it is 

 plain that the range of their vision is very limited. Any one who 

 has noticed the light and jerky flight of a butterfly approaching a 

 wall, must have seen it almost knock its head against it before it 

 discerns it. It then falls back a little and lilts away upwards, 

 again approaches the wall, again discovers the obstruction, makes 

 another slight retreat and upward flight, and goes through the 

 same operation until it reaches the top. The reason why we see 

 the crushed remains of the "shard-born beetle" so often lying 

 on the pathway is from their knocking themselves down, by com- 

 ing against the passer-by or other obstructions, as they wing their 

 drowsy flight. We could cite a multitude of other incidents to prove 

 the absence of far-sighted vision in insects ; and, of course, if that 

 really be the case it is impossible that gaudy colours, which they 

 cannot see, can be given by nature to flowers for the purpose of 

 attracting them. It may be said that although this infirmity of 

 vision may exist in some insects, it may not be present in all. 

 Some have large eyes, and some small, and some none at all, so 

 that there must be various degrees of vision. We quite admit 

 this ; but what we say is, that the kind of vision is the same in all; 

 the plan of the optical apparatus is constructed on the same prin- 

 ciple in all, and that an inferior principle, and one with less scope 

 and shorter focus, than the plan of the eye in the higher animals. 



We are less disposed to dispute the supposed final purpose of 

 the nectary and its secretion (honey). Insects seem to have the 

 sense of smell developed to a much higher degree than that of 

 sight or any other sense. The multitudes attracted almost instan- 

 taneously by the presence of any putrifying matter, the crowds of 

 males drawn in the darkness of the night to the entomologist's 

 window when he places there a virgin female of the same species, 

 and a multitude of other instances to the same purport, sufficiently 

 shew that that sense is possessed by insects to a degree of acute- 

 ness far beyond what we enjoy. The supposition, therefore, that 



