i84 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 less specialized flies — 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 



