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 reins 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 biting 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 allies, and has never been observed stealing nectar, while 
B. terrester, 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 (‘ Beitrige,’ 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 :— 
Percentage | Number of 
Length of Proboscis of species with 
Name of Bee. 9 sid % perforations | perforated 
made. flowers. 
mm. mm. 
Bombus mastrucatus Gers. . . | 10-13 g-II 50 51 
Pe URRIERICE le ee fav ahs. ap Q-I1'5 8-9-75 35 125 
RS IAI ATE PSs os) oe a Q:5-I2 40 
B. pratorum Z, . . 12-14:5 | 8-5-12 24 
B. Rajellus X,. (B. ibibinetie) 13-14 II-13 19 
Apis mellificaZ.. . . . . . — 5°5-6°5 II 
Bombus alticola Kriechb.. . . | 10-13 Q-II-5 15 1I 
B. soroénsis /adr. var. Proteus 
Gerst. (and others) . . .| 13-14 10-13 9 
B.lapponicus abr. . « «=| 12-13 g—-12 7 
B. mesomelas Gersti . . . «| 15-18 12-14 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 
elongation 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 Miiller 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 difficult. 
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 Z. and the 
Perforation of Flowers,’ Trans. Acad. Sci., St. Louis, Mo., v, 1888, pp. 241-77), States 
