184 INTRODUCTION 
to be highly specialized flower visitors, this is not the case with the lower Diptera— 
the Muscidae, gnats, and the like. The selection of flowers by these forms is generally 
irregular, inconstant, and erratic, so that Hermann Miiller’s observations differ con- 
siderably from those of E. Loew. According to my own investigations (op. cit.), short- 
tongued flies (Muscidae, and others) prefer flowers with exposed nectar, which is 
conveniently situated for them, to as great a degree as the short-tongued wasps, 
which stand on a similar level as regards adaptation to flower pollination. They 
too are attracted by conspicuous social flowers, especially those which are white or 
yellow. Half-concealed nectar is somewhat too deep for them, so that they pay but 
slight attention to flowers presenting it. In their other visits to flowers they confine 
themselves almost exclusively to stealing pollen. 
Although among the “ess sfectalized flves—i.e. Diptera other than Bombyliidae, 
Conopidae, Syrphidae, and Empidae—there are some species, genera, and even 
branches of families that are very constant in their visits to flowers, e.g. among the 
Dolichopidae, Stratiomyidae, and especially the Muscidae (Gonia, Ocyptera, and 
Prosena, with a much elongated proboscis), they are nevertheless insignificant in 
number and importance, compared with the hundreds of more stupid species with 
shorter proboscis. Among these Diptera that are less capable of pollinating flowers, 
the visits paid in the Alps to white and yellow blossoms are far more numerous than 
those to red, violet, and blue ones. But here again in comparing families or sub- 
families that are constant or inconstant in flower selection, and possess respectively 
a long or a short proboscis, it becomes plainly evident that with increasing capacity 
for flower pollination the preference for red, blue, and violet becomes more and 
more marked, while the liking for flowers with exposed nectar correspondingly 
diminishes (H. Miiller, ‘ Alpenblumen,’ pp. 515, 518). 
D. Beetles (Coleoptera). 
The Coleoptera exhibit (Herm. Miiller, ‘Fertilisation,’ pp. 32-6) unequivocal 
adaptations to procuring flower-food. They are of importance for pollination since 
many species belonging to widely different families seek out flower-food in addition 
to other nourishment, and a still greater number are entirely anthophilous. Although 
none of our native plants are pollinated by beetles exclusively or even chiefly, yet 
these insects largely co-operate in the discharge of this office for many flowers. 
The numerous species of the genus Meligethes are so small that they can creep into 
most flowers, and in many cases transfer pollen. On the other hand, beetles greatly 
damage many flowers by devouring the anthers and other structures. 
In flowers with exposed nectar (Umbelliferae, Cornus, Parnassia), continues 
Herm. Miiller, many species of beetles may be seen licking it; also in flowers with 
exserted stamens and nectar which though concealed is accessible to very short- 
tongued insects (Rosiflorae, Compositae), beetles may be seen licking up nectar, 
devouring pollen or anthers, or even gnawing the petals and pistils. In flowers with 
conspicuous anthers, and either devoid of nectar or with this too deeply concealed 
(Ranunculaceae, Plantago), beetles feed upon the pollen, the anthers, and other soft 
structures. Flowers which afford shelter from wind and rain (Campanula, Digitalis) 
are also visited by beetles, which devour the pollen and soft tissues. In more 
