164 



INTRODUCTION 



lesser degree they show preference for flowers with concealed nectar (Knuth, 

 ' Bliitenbesucher,' II, p. 10). 



Humble-bees differ as regards the flowers they visit according to the length of 

 their proboscis. The longer this is, the more exclusively do they seek out flowers 

 belonging to Class H ; the shorter it is so much the more do they also visit flowers 

 with less deeply concealed nectar, and show an increasing disposition to steal nectar 

 by biiing holes. Bombus hortorum, which has a longer proboscis than any other 

 of our native humble-bees, shows a more decided preference for the flowers of 

 Class H than any of its alhes, and has never been observed stealing nectar, while 

 B. tenester, our shortest-tongued species, is especially fond of biting through corolla- 

 tubes, in order to steal nectar through the openings thus made. The hive-bee often 

 steals nectar through holes bitten by this and other species of humble-bee. 



A. Schulz (' Beitrage,' II, pp. 203-24) names 165 species of plants with flowers 

 thus bitten through which he has observed in the lowlands and in the Alps. The 

 following table summarizes his observations on bees which treat flowers in this 

 way : — 



Na7ne of Bee. 



Bombus mastrucatus Gerst. . . 



B. terrester L 



B. lapidarius L 



B. pratorum L 



B. Rajellus K. (B. derhamellus) . 



Apis mellifica L 



Bombus alticola Kriechb. . . . 



B. soroensis F'adr, var. Proteus 



Gersi. (and others) . . . 



B. lapponicus J<'a6r 



B. mesomelas Gerst. .... 



Length cf Proboscis 



in 



? 5 



mm. 

 10-13 



9-II-5 

 12-14 

 12-14.5 

 13-14 



10-13 



13-14 

 12-13 



15-18 



mm. 

 9-1 1 



8-9-75 

 9-5-12 

 8-5-12 

 11-13 

 5-5-6-5 



9-1 1-5 



10-13 



9-12 



12-14 



Percentage 



"f . 

 perforations 



made. 



50 

 35 



15 



Number of 



species with 



perforated 



flowers. 



51 

 125 

 40 

 24 

 19 

 1 1 

 I I 



9 



7 

 I 



Except, therefore, in Bombus mastrucatus, we see that the tendency to perforate 

 flowers diminishes as the length of proboscis increases, the explanation being that 

 elongaiion increases the possibility of obtaining nectar in a normal manner from 

 deeper flowers. Among seventy-six visits of Bombus mastrucatus to various flowers, 

 observed by Hermann MUller in the Alps, there were thirty-four cases of nectar 

 theft. This humble-bee — called by Miiller (Kosmos, v, p. 422) 'an anti-teleologist 

 among the visitors of alpine flowers' — is distinguished ('Alpenblumen,' p. 586) 

 above all others, even B. terrester, by its very decided habit — an unfortunate one for 

 flowers — of biting holes in order to get at the nectar of deeply placed nectaries 

 to which access is difiicult. 



F. Ludwig, in his review (Bot. Centralbl., Cassel, xxxvii, 1889, pp. 355—7) of 

 a memoir by L. H. Pammel (' On the Pollination of Phlomis tuberosa L. and the 

 Perforation of Flowers,' Trans. Acad. Sci., St. Louis, Mo., v, 1888, pp. 241-77), states 



