HYMENOPTERID FLOWERS 



117 



through the holes bitten by this humble-bee. In the Alps, Bombus mastru- 

 catus Gersi. is distinguished above all other humble-bees ' by its constant habit 

 destructive to the flowers of getting nectar by forcing an entrance to deep and not 

 easily accessible nectaries.' 



Lepidoptera here again behave as in Bee Flowers proper. Other visitors are 

 almost without exception pollen-thieves (Knuth, ' Bliitenbesucher,' II, pp. 6 and 7). 



Hermann Miiller ('Alpenblumen,' pp. 499 et seq.) has dealt very thoroughly with 

 the colours of Bee Flowers and Humble-bee Flowers. He calls attention to the 

 fact ih-AX flowers of this class which are in bloom at the same time and place, are as a 

 rule of diverse colours. Miiller recalls the circumstance that several species of the same 

 genus, with exposed or only partially concealed nectar, are often in flower beside one 



Fig. 27. Humble-bee Flowers. (i!i Salvia pratensis Z^., a Humble-bee Flower with lever mechanism. 

 (2) Medicago sativa Z,., a Humble-bee Flower with spring mechanism. 



another at the same time, and possess the same hue, e.g. Ranunculus acris, bulbosus, 

 and repens. Even, however, in the case of flowers with completely concealed nectar, 

 accessible to short-tongued insects, similarly coloured species are in flower together, 

 e.g. Sempervivum, Mentha, and numerous Compositae (especially Cichoraceae). 



The colour relations between closely allied Bee Flowers blooming simultaneously 

 in the same district are, on the other hand, of quite a diff'erent nature. Hermann 

 Miiller contrasts the following species with one another' : 



Aconitum Lycoctonum yellow ; A. Napellus blue ; 



Lamium album white ; L. maculatum red ; Galeobdolon luteum yellow. 



Salvia glutinosa yellow ; S. pratensis blue. 



Teucrium montanum -white ; T. Chamaedrys purple. 



Pedicularis tuberosa whitish-yellow ; P. verticillata purple. 



Trifolium badium yellow to brown ; T. montanum small white capitula, 

 standing high; T. repens larger white capitula, standing low; T. pratense var. 

 nivale still larger, dirty white capitula ; T. alpinum purple. 



' Frank ( ' Untersuchungen iiber die Farben der Bluten,' p. 30, Tiibingen, 1825) long ago called 

 attention to such contrasts in colour between related species : these two contrasted colours, i. e. 

 blue and yellow, he says, frequently appear in different species of the same genus, e. g. the genera 

 Linum, Scabiosa, Aconitum, Lupinus, Iris, and others, include species with pure blue and pure 

 yellow flowers. 



