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remember how its action has effected the aspect of life on our planet 
more than any other force of the same order. The whole of our 
flowering plants, and a very large number of our insects, owe their 
existence to the way in which plants found it profitable to encourage 
the visits of insects desirous of robbing them, first of their pollen, but 
now chiefly of their honey. 
Many plants again found that animals feeding on their seeds were 
useful as disseminating them, and grew more and more suitable seeds 
accordingly. They found also that by attracting them, not to the seeds 
but to surrounding pulp, etc., the services were more cheaply obtained. 
Hence originated fruits as distinguished from seed-vessels. Many animals 
thus became professional agriculturists and horticulturists, without, 
however, of course, having any consciousness of what they were really 
doing. When man, however, who had no doubt been employed in 
this manner for ages, acquired the final human characteristic of 
conscious reason, he began the definite process, by which both be, and 
the animals and plants on which he preys, have so largely profited, and 
which results in the latter, and especially the cereals and the ruminants, 
occupying such a disproportionately large share of the earth s surface. 
There are many other forms of this beneficial inter-relationship, of 
which I may refer to one, as being that of a moth, viz., the Yucca moth, 
whose life history and economy has been so well worked out by Riley. 
The benefit conferred by the moth is in fertilising the flowers, not 
apparently as a secondary result of a desire to feed herself, but of set 
purpose, as if she knew what she was doing. This appears especially 
to be so, since the Yucca is practically never fertilised in any other 
way, and yet, since her larvae feed on the seeds, they would have no 
food unless she carefully attended to the fertilisation of the plant. I 
may say that this moth is one I have often wished I could have an 
opportunity of observing, since it is an Adelid, yet more strongly 
reminds one of Eriocraniids in some respects, and as regards its pollen 
collecting habit, recalls very definitely the procedure of Micropteryx, 
in eating the pollen of the flowers it visits. Since its host the Yucca 
is rather low amongst the flowering plants, we may have here, 
preserved and specialised, one of the earlier stages in the combined 
evolution of moth and flowering plants, beginning with what we still 
have a (no doubt modified) representative of, viz., the Micropteryx in 
a Carex or Luzula. 
As regards the Tortrix unicolorana, I have suggested already that 
where the° attack would not be beneficial to the Asphodel the plant 
had some means of repelling the attack and so won freedom from it. 
This is merely another way of saying that when the attack is 
beneficial, the plant is in some way able to invite it. How, it is 
difficult to suggest. 
Reflecting how accidental was my appreciation of this relationship 
between the plant and the caterpillar, and of what an unusual nature 
the benefit conferred on the plant is, and what many conceivable 
forms such benefits may take, it does not seem quixotic to assume that 
there are probably a good many other such cases still waiting to be 
observed and understood, possibly some others are already known, 
though I have not heard of them, or if I have, have forgotten them. 
