On Plants and Insects. 1 59 



aphides and cocci secure immunity from the attacks 

 of the ants, but even turn them from foes into 

 friends. They are subject to the attacks of a 

 species of ichneumon, which lays its eggs in them ; 

 and Delpino has seen ants watching over the scale 

 insects with truly maternal vigilance, and driving 

 off the ichneumons whenever they attempted to 

 approach. 



7. But though ants are in some respects very 

 useful to plants, they are not wanted in the flowers. 

 The great object is to secure cross-fertilisation ; but 

 for this purpose winged insects are almost necessary, 

 because they fly readily from one plant to another, 

 and generally, as already mentioned, confine them- 

 selves for a certain time to the same species. 

 Creeping insects, on the other hand, naturally would 

 pass from each floret to the next ; and it is of little 

 use to bring pollen from a different flower of the 

 same stock ; it must be from a different plant alto- 

 gether. Moreover, creeping insects, in quitting a 

 plant, would generally go up another close by, with- 

 out any regard to species. Hence, even to small 

 flowers, which, as far as size is concerned, might 

 well be fertilised by ants, the visits of flying insects 

 are much more advantageous. Moreover, if larger 

 flowers were visited by ants, not only would these 

 deprive the flowers of their honey, without fulfilling 

 any useful function in return, but they would pro- 

 bably prevent the really useful visits of bees. If 

 you touch an ant with a needle or a bristle, she is 



