52 ANGIOSPERMAE—DJCOTYLEDONES 



than allied species native to the regions mentioned : that of B. hortorum is 2 1 mm. 

 long, and that of B. Gerstackeri 22 mm. Alfken tells me — in a private letter — that, 

 when ascending the Schlem in the Tyrol, he noticed large numbers of B. hortorum 

 L. (j and 5) with B. Gerstackeri Mor. (5) on the flowers of A. Lycoctonum, diligently 

 sucking nectar. 



In Jamtland (Sweden), Aurivillius observed B. hortorum Z., and frequently B. 

 consobrinus DaUb. as well. The latter resembles the former so closely that 

 Schmiedeknecht describes it as a variety of this (' Apidae Europ.,' pp. 295, 297, 305). 



MacLeod — in the Pyrenees — also met with B. hortorum Z. as a visitor of A. 

 Lycoctonum Z., var. pyrenaicum Ser. (=A. pyrenaicum). The same observer 

 further noticed many individuals of B. Gerstackeri Mor. 5, sucking nectar from this 

 flower, and effecting cross-pollination. 



From these observations it appears that A. Lycoctonum Z. is everywhere visited 

 and pollinated by humble-bees with a proboscis of exceptional length. In the Alps 

 and Pyrenees, however, B. mastnicatus Gerst. has been observed on the flowers 

 either collecting pollen, or perforating the upper sepal at the level of the nectary, 

 in order to steal nectar. Both in Central Germany and in Sweden, short-tongued 

 humble-bees have been observed as nectar-thieves, e. g. B. terrester Z. and B. alticola 

 Kriechb. In Sweden, B. jonellus K. (=B. scrimshiranus K^ has been seen collecting 

 pollen. 



Aurivillius and MacLeod observed (in Sweden and the Pyrenees respectively) 

 two very well-marked kinds of flower, between which transitional forms were fotmd 

 here and there. They may be described as : — 



(a) orthocera Knuth : spur almost straight, relatively stout, with blunter tip ; 



(3) campylocera Knuih: spur more or less distinctly curved upwards — some- 

 times into almost a semicircle — relatively slender, tapering towards the tip. In the 

 bud the spur of this form also is straight. 



104. A. anthora L. (MacLeod, ' Pyrenegnbl.') — The pale yellow flowers open 

 wide. The upper sepal is produced above the mouth of the flower into a forwardly 

 curved beak. The two lateral sepals are concave internally and clothed with woolly 

 hairs. The two or three other floral leaves serve as alighting-places and platforms 

 for insects. The black stamens are sharply defined against the otherwise uniform 

 colour of the flower, which is thus made very conspicuous. The stamens and carpels 

 develop in the same order as in A. Napellus. But few stamens mature simul- 

 taneously, so that the flower remains for a long time in the male condition. 



Visitors. — None were observed by MacLeod. Hoff'er noticed — at Graz — 

 Bombus Gerstackeri 5, sucking. 



105. A. septentrionale KoelL — Axell states (' Om anord. f. fanerog. vaxt. 

 befrukt.,' Stockholm, 1869, p. 34) that this species also is protandrous. 



A. Napellus — at least so far as observations have been made — and there is thus, at least apparently, 

 a real diflerence as to diet (according to Hoffer, Natw. Miscell., 1889, pp. 21-2). HofTer (op. cit., 

 pp. 23-5) noticed in Steiermark, however, that in places where A. Napellus is very common, while 

 A. Lycoctonum is exceedingly rare, B. Gerstackeri o also visits A. Napellus, so that the heterotrophy 

 observed by Ualla Torre on the Schlern in the Tyrol does not there exist ; all castes (o, b, and J) 

 feeding chiefly on A. Napellus. 



