200 INTRODUCTION 



must then be already prepared to make observations. It is in the early morning that 

 insects are to be seen in abundance on many flowers, which later on seem dead and 

 empty, since their mechanism for securing pollination has been put in action, and 

 they have been plundered of their insect food. Sprengel says ('Entd. Geh./ p. 23), 

 ' It is especially the midday hours when the sun high up in the unclouded heavens 

 makes it warm or even hot which are the time for making diligent observation. 

 The day flowers then appear in their greatest beauty, and with all their charms tempt 

 insects to visit them, and at this time their fertilization can the more readily be 

 effected because the pollen of such anthers as are exposed to the air is quite dry. 

 But it is precisely during these hours that insects liking as much heat as possible 

 are most active in and upon the flowers, their aim being to gorge themselves with 

 nectar, while at the same time they fulfil the design of Nature by effecting fertiliza- 

 tion. In the realm of Flora, whose wisdom is no less admirable than her beaut}-, 

 wonderful things take place at this time, of which the chamber-botanist who 

 is meanwhile busy with his breakfast has not the faintest idea.' 



Hermann Miiller (' Alpenblumen,' p. 547) makes the following remarks about 

 the visits of insects to flowers in the Alps. ' While in still weather and warm 

 sunshine there is usually an abundance of insects visiting flowers, corresponding 

 to their profusion, a cool breath of air is often sufficient to drive away most of the 

 floral guests especially the Lepidoptera into their hiding-places. On the other 

 hand, when calm, sunny weather suddenly relurns after a few cold and windy days 

 of fog and rain, increased activity is seen among the insects which fertilize flowers. 

 The longer they have had to remain hungry, the more busily and persistently will 

 they seek for flower-food, and the blossoms which after several days' waiting have at 

 last opened to the warm rays of the sun, are now for the most part fertilized.' 

 These words are not merely true for alpine flowers and insects, but are of universal 

 application. 



Beetles, most Bees and Lepidoptera, and also Hover-flies, permit of close approach 

 during their visits to flowers, so that their movements can be accurately seen, and 

 even the act of pollen transfer be observed. Other flies, especially Muscidae, are 

 often so timid that they fly away at once when any one approaches the flowers in 

 which they are busy, or they avoid settling on a flower when any one is near. In 

 such cases it is necessary to watch the movements of these timorous guests through 

 a telescope, preferably from a somewhat elevated position, or while lying on the 

 grass. 



Observations should be made as far as possible in the natural habitat of plants, 

 as here the flower mechanisms and flower guests are in the original state, while 

 a garden plant may have undergone slight modifications in its flower mechanism, 

 while its visitors can only be recruited from insects which live in the garden or its 

 vicinity. A pot plant or cut flower in a room can of course only occasionally be 

 visited by insects which fly through the open window, and its flower mechanism 

 may then deviate very considerably from what is natural (cf. my note on Parnassia 

 palustris in vol. II). On this point Sprengel ('Entd. Geh.') speaks as follows: 

 ' We shall certainly not discover Nature's plan in the structure of flowers by taking 

 the plant out of the garden or country. We must rather study flowers in their 

 natural habitats in short, we must try to surprise Nature in the act' 



