26 THE FERTILISATION OF FLOWERS. [PART I. 
I have been unable to pay equal attention to all groups of 
anthophilous insects. I could neither determine by myself the 
minute flies and gnats, ichneumon-flies and their allies, aphides 
and species of Meligethes and Thrips, nor could I get them reliably 
determined by others; these, accordingly, along with most ants 
and some saw-flies, are referred to only in general terms. Noc- 
turnal lepidoptera and microlepidoptera are left almost untouched 
for another reason, viz. the difficulty of observing them upon 
flowers in the dim light. On the other hand, I have paid close 
attention to the beetles, the larger flies, bees, ‘wasps, and butterflies, 
and I have determined their species with the aid of the entomo- 
logists referred to in my preface. But just on account of this 
simultaneous observation of so many insect groups, in the case of 
the most frequented flowers it is probably only the commonest 
species that have fallen into my hands; so that it will be easy 
for any collector of a special group to show the most extensive 
omissions in my richest lists. I indeed hope that this may be done 
on the largest scale. 
In hastening to publish provisionally an account of my researches, 
it was further impossible for me to follow out thoroughly in the 
case of all the: groups of anthophilous insects the modifications 
which fit them for a floral diet, and to prove that such modifica- 
tions have been evolved gradually. In thecase of bees, the most 
important visitors of flowers, I have attempted to give such 
proof in a special work. In the present book I must limit myself 
to giving a general account of the adaptations of insects to the 
flowers visited by them, so far only as seems essential for a right 
understanding of the actions of insects upon flowers. 
NOTES ON THE HISTORICAL INTRODUCTION, 
1. Severin Axell gives in his work (17), published in 1869, a short review of 
the development of our knowledge of the sexual relations of plants. He 
says :— 
“ Although we meet even in ancient Greek and Roman authors with dim 
foreshadowings of the sexuality of some diclinic plants, it is only towards the 
end of the seventeenth century that we find the existence of two sexes in the _ 
higher plants clearly and generally acknowledged. In 1682, Nehemias Grew 
published his book The Anatomy of Plants, in which he maintained the 
necessity for the pollen to act upon the pistil to form the fruit. Rud. Jac. 
Canierarius? and Sebastian Vaillant? strongly supported the new views, partly 
1 Epistola de sexu plantarum (Tiibingen : 1694). 
* Discowrs swr la struetwre des flewrs, ete. (Paris: 1717). 
