106 INTRODUCTION 
White or Fellowish-white: Anemone nemorosa, sylvestris, narcissiflora; Spiraea 
Ulmaria,Aruncus Filipendula; Sambucus nigra, racemosa; Cistus salvifolius, and others. 
Fellow ; Anemone ranunculoides and alpina; Chelidonium majus, Hypericum 
perforatum, Papaver alpinum, Helianthemum vulgare, Lysimachia vulgaris, Verbas- 
cum Thapsus, Narthecium ossifragum, and others. 
Red: Papaver Rhoeas, Rosa, and others. 
Lilac or Violet: Thalictrum aquilegifolium, Solanum Dulcamara. 
Blue: Hepatica triloba. 
As I have demonstrated (op. cit., p. 11), the visitors of white, yellow, and also 
red pollen flowers are chiefly bees and hover-flies with a short proboscis. The 
bodily structure and the habits of these insects sufficiently explain this fact. 
concealed honey is not accessible to bees with a short proboscis, and therefore they 
not only eagerly visit flowers with exposed or partly concealed nectar, but also 
pollen flowers yielding a rich booty of pollen. This substance forms a very impor- 
tant article of food for them, and they often carry it away from pollen flowers in 
great balls on their collecting-apparatus. The same holds true for hover-flies, which, 
as regards length of proboscis, and fitness for pollinating flowers, present the same 
stage of adaptation as short-tongued bees. They too are excluded from the enjoy- 
ment of nectar that is completely hidden, and pollen, which they find most abundantly 
in pollen flowers, is a kind of food they doubtless covet as much as nectar. It is not 
surprising to find honey-bees, the most energetic and industrious and perhaps the 
commonest of all floral visitors, upon many pollen flowers. Some humble-bees 
also, and various other long-tongued bees, settle upon pollen flowers, especially those 
which are red, violet, or blue, and load their hind-legs with pollen. The parasitic 
humble-bees (Psithyrus), which are devoid of a basket, and consequently incapable 
of collecting pollen, are not met with upon pollen flowers. In the Alps, where 
lepidoptera are numerous, they also occur as floral guests, always seeking in vain 
for nectar, and usually flying away after a short visit, now and then, perhaps, boring 
into the tissue of the base of the flower, and thus getting at some sap. Muscidae 
also are among the visitors, likewise seeking nectar in vain, but owing to their small 
perceptive powers, always coming back again. Lastly, beetles may at times appear 
as common floral guests, which regard the abundant pollen as welcome booty. 
Visitors belonging to other groups of insects do not fall to be considered in this 
general account. 
In some pollen flowers the filaments are closely beset with hairs (Verbascum, 
Anagallis, Narthecium, Tradescantia), which often display conspicuous colours, and 
serve not only as pollen-guides to insects, but also as supports and footholds during 
their labour. Flowers of this kind are preferred by pollen-collecting bees. 
Bee flowers too are those pollen flowers in which the anthers are united into 
a yellow cone closely surrounding the style and presenting a marked contrast of 
colour with the violet petals, e.g. Solanum Dulcamara and species of Cyclamen. 
The bee clambering over this anther-cone opens it, and is dusted with the dry 
powdery pollen that falls out. These flowers (along with nectarless lepidopterid 
flowers) represent the highest stage of the present group. 
That Macropis labiata visits Lysimachia vulgaris almost exclusively has already 
