HYMENOPTERID FLOWERS 119 



Lycoctonum Z. var. pyrenaicum Ser. in the Pyrenees. It may be added that this 

 observer also saw many individuals of Bombus Gerstaeckeri Mor. ? seeking the 

 nectar of this flower. This species (Schmiedeknecht, ' Apidae Europ.,' p. 304) is 

 identical with B. opulentus Gersi. (Knuth, ' Blutenbesucher,' II, p. 7). 



Another instance is aflforded by Corydalis solida and C. cava. The only 

 nectar-sucking insect effecting cross-pollination, and observed on the two species 

 of Corydalis (by Herm. MuUer in Lippstadt, by myself in Kiel, and by MacLeod in 

 Ghent) was Anthophora pilipes J and ? , which with its long proboscis (19-21 mm.) 

 can conveniently reach the nectar secreted and concealed in the base of the spur. 

 ' It visits the Corydalis flowers in such numbers and so diligently that it suffices for 

 the pollination of all of them.' Hermann Muller further observed two hairy hover- 

 flies (Bombylius major L., and B. discolor Mgn) sucking in the normal way, 

 though they were only nectar-thieves, and did not liberate the floral mechanism. 



It is also known that Cerinthe alpina is pollinated exclusively by Bombus 

 alticola, and Delphinium consolida by B. hortorum. 



An intermediate stage between Bee Flowers and Humble-bee Flowers is con- 

 stituted by Bee-Humble-bee Flowers (Hbh) which, e.g. in Calamintha alpina, 

 possess two different floral forms, one of which is regularly visited by humble-bees 

 only, while the nectar of the other is accessible even to bees with a proboscis less 

 than 7 mm. long. In this species, according to Hermann Muller ('Alpenblumen,' 

 pp. 319 and 320), there are large-flowered and small-flowered stocks, both of them 

 hermaphrodite and protandrous. In the flowers of the former the corolla-tube is 

 10 mm. long, in those of the latter it is only 6 mm. The relations are similar 

 in the case of Alectorolophus major and minor, which Hermann Muller regards 

 ('Fertilisation,' pp. 454-6) as different forms of one species (Rhinanthus Crista- 

 galli Z.). The corolla-tube in ' major ' is 9-10 mm. long, in ' minor ' 7-9 mm. 



Wasp Flowers (Hw) also permit other insects to reach their nectar, and may 

 be pollinated by them. They have, therefore, already been mentioned among flowers 

 with concealed nectar to which they belong, so far as the shelter of nectar is 

 concerned. 



In many regions the visitors of Symphoricarpos racemosus Michx. are mostly 

 True Wasps. Hermann Muller ('Fertilisation,' p. 292) observed that irt Thuringia 

 more than nine-tenths of all the visitors belonged to five species of Vespidae, while 

 in Westphalia, where wasps are less abundant, the visits of honey-bees were more 

 numerous. I myself noticed in Thuringia that Vespa saxonica was very commonly 

 to be seen sucking nectar from snowberry flowers, while in Schleswig-Holstein (chiefly 

 on the North Sea coast, and the Baltic coast from Riigen to Geestemunde) I 

 observed that the visitors and pollinators of this plant ' were almost exclusively bees 

 and humble-bees. Scrophularia nodosa is a much more characteristic wasp flower. 

 Not only in Europe, but also in North America, wasps have been noticed as the 

 most important floral visitors of this plant. It appears, however, that this visitation 

 is not uniform at all times of the year. In Holstein, for example, I found that this 



' After the completion of my manuscript, I saw on July 20, 1897, at Heringsdorf, in the 

 Island of Usedom, that Symphoricarpos racemosus was visited by numerous sucking species of wasps, 

 as well as by Apis and Bombus lapidarius L. 5 . 



