RANUNCULACEAE 



51 



Kronfeld states that Handlirsch observed eight species of humble-bee in lower 

 Austria, and Hoffer ten in upper Austria, those with a short proboscis (B. mastru- 

 catus, B. terrester, B. soroensis, and B. mendax) obtaining the nectar by perforatin'- 

 the flowers. " 



102. A. variegatum L. — 



Visitors.— Kronfeld— in Austria — saw Bombus agrorum (5 and 5) and B. 

 hortorum (5, 5, and S) sucking legitimately, also Halictus morio and other short- 

 tongued insects vainly seeking for nectar. Schulz observed perforated flowers of 

 this species in Thuringia. 



103. A. Lycoctonum L. (Sprengel, 'Entd. Geh.,' p. 279; Herm. Muller, 

 ' Alpenblumen,' pp. 139-40; MacLeod, ' Pyreneenbl.' ; Aurivillius, C, 'Uber d. Bl. 

 u. Befrucht. v. Aconitum Lycoctonum L.,' Bot. Centralbl., Cassel, xxix, 1887, 

 pp. 125-8; Kronfeld, ' Uber d. biol. Verhaltn. 



d. Aconitumbliite,' Bot. Jahrb., Leipzig, xi, 

 1889; Loew, ' Blumenbesuch,' I, p. 28; 

 Knuth, ' Bliitenbesucher '). — This agrees 

 essentially with the species already de- 

 scribed in the structure of its flowers, but 

 the nectar is so deeply placed as to be 

 only accessible to humble-bees with a very 

 long proboscis. The upper sepal of the 

 yellow blossom is an almost vertical cylinder, 

 which serves as a protective envelope for 

 the nectaries. Each of these is produced 

 into a spiral tube (of one and a half turns), 

 which is full of nectar, that is here secreted 

 very abundantly. The stalk of the nectary 



is about 20 mm. long, and a proboscis 



Fig. 20. Aconihtm Lycoctonum, L. (after Hernt. 

 Muller). A. Flower in the second (female) condi- 

 tion ; seen from the side. Natural size. B. Loniji- 

 tudinal section of the same (nearly twice natural 

 size). The upper stamens have already fallen off. 



of about the same length is necessary for 

 sucking, as humble-bees can get no foot- 

 hold in the cylindrical sepal, but are obliged 

 to cling to the stamens and carpels. 



Visitors. — In Central and North Germany the yellow monkshood is visited 

 exclusively by Bombus hortorum L. ; in the Alps almost solely by B. opulentus 

 Gerst. ( = B. Gerstackeri Mor.)''. These two humble-bees have a longer proboscis 



' Frey-Gessner (' Exkursionen im Sommer 1880,' Mitt. Schweiz. Ent. Ges., vi, 1881) first pointed 

 out that the old o of Bombns Gerstackeri Mor. consistently alights upon Aconitum Lycoctonum L., th^ 

 5 and o upon A. Napellus Z.. and this phenomenon has been described by Dalla Torre as hctero- 

 trophy (cf. vol. I, pp. 160-1). This investigator explains the adaptation as due to the extremely short 

 working period of this humble-bee, which only appears in July, and of course disappears at the end 

 of September or beginning of October, and to the fact that ^ and o appear simultaneously with 

 the foundress-queens (from Aug. 20 on), so that it is in the interest of the species that they should 

 visit different flowers. The term ' heterotrophy ' (ert/iot, different ; Tpo<pi\, food) is reasonable in so 

 far that in districts where A. Lycoctonum and A. Napellus occur side by sid; in great profusion, the 

 of B. Gerstackeri appears actually only to visit A. Lycoctonum, the ^ and o on the other hand only 



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