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 beauty, 
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 returns 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 Musczdae, 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 tn the act, 
