FLOWERS WITH EXPOSED NECTAR 



109 



In accordance with the position of the nectar, flowers of this class are chiefly 

 visited by insects with a short proboscis : short-tongued wasps and flies predominate, 

 but to these must be added beetles with equally short proboscis, and flies (Syrphidae) 

 with proboscis of medium length, and more rarely bees with proboscis of medium 

 length. All other insects are relatively unimportant. Even the honey-bee, so active 

 everywhere else, is seen here comparatively seldom : apparently the small quantity of 

 pollen and nectar off'ers it too little attraction, and even less to its allies with still 

 longer proboscis. Lepidoptera, in which the long proboscis is ill-adapted for sucking 

 up the flat layer of nectar, are extremely rare guests, even in the Alps, where such 

 insects abound. (Cf. Knuth, ' Die Besucher derselben Pflanzenart in verschiedenen 

 Gegenden,' I, p. 13.) 



ryi 



Fig. 20. Flowers with exposed 7iecla7: (i) PImpinella rubra ^(j//^. 



(3) Gentiana lutea L. n. Nectary. 



(2) Saxifraga aspera L. 



Hermann IMiiller ('Alpenblumen,' pp. 481-4) arrives at similar conclusions with 

 regard to alpine flowers with exposed nectar : those which are pure yellow, yellow 

 with orange spots, greenish-yellow, or white, are principally visited by short-tongued 

 insects (85 % of the visitors), in particular by Muscidae, while bees and Lepidoptera 

 are relatively very infrequent (only 15 %). The same also holds for the reddish 

 Umbelliferae (Meum INIutellina, Pimpinella rubra), while the more intensely red 

 Azalea procumbens, which secretes nectar abundantly, is mainly visited by floral 

 guests with a more specialized sense of colour, i.e. Lepidoptera, bees and hover- 

 flies (80 % of the visitors), while INIuscidae are less numerous (20 %). In many 

 species of Saxifraga, in Veratrum, and in Lloydia, the insect guests are so pre- 

 dominantly Diptera, that Hermann Miiller (op. cit., p. 483) united them into 

 a special group distinguished by the symbol A D (Fly flowers with fully exposed 



