RANUNCULACEAE 47 



but which is no longer on the wing when the field larkspur comes into flower — 

 a number of species with a proboscis 15 mm. in length (cf. vol. I, p. 160), but 

 Bombus hortorum Z. — with a proboscis 17-21 mm. long — is alone able to reach 

 the nectar without considerable loss of time, the other species being compelled to 

 force their heads between the four petal-lobes that form the entrance. Wherever 

 observations have been made on the guests of Delphinium consolida (Westphalia, 

 Thuringia, Schleswig-Holstein), this humble-bee has been shown to be the normal 

 visitor and pollinator. It flies with the greatest industry from flower to flower, 

 steadily effecting cross-pollination, and receiving all the nectar in return. Occasion- 

 ally, indeed, other guests appear, especially Lepidoptera (species of Vanessa, Pieris, 

 Satyrus, Hesperia), which usually reach the nectar with their long thin proboscis 

 without touching stamens or carpels. I sometimes saw the honey-bee — the proboscis 

 of which is only 5-7 mm. long — visiting the flowers and vainly seeking for nectar, 

 thrusting its proboscis into the spur, and therefore now and then eff'ecting cross- 

 pollination. In Thuringia, Schulz observed spurs perforated by nectar-thieves, no 

 doubt short-tpngued humble-bees, though he was not able to catch the plunderers 

 in the act. In the same part of Germany, Hermann MilUer also noticed B. lapi- 

 darius L. sucking. Schletterer — at Pola — saw the bee Anthidium manicatum L. 

 as a visitor. 



99. D. Ajacis L. (Sprengel, 'Entd. Geh.,' pp. 277-8; Knuth, ' Blutenbiol. 

 Herbstbeob.') — The flowers agree in structure with those of the last species. The 

 length of the spur in garden plants at Kiel was 15-18 mm. 



Visitors. — As a regular visitor and pollinator, I observed Bombus hortorum Z., 

 and as an occasional visitor the honey-bee, which of course did not succeed in 

 reaching the nectar. As a nectar-thief, I now and then noticed Vanessa lo. Z. 



100. D. grandiflorum Jord. — Jordan states that the anthers of the posterior 

 stamens are directed forwards, while those of lateral and anterior stamens are 

 directed laterally outwards. 



22. Aconitum Toum. 



Literature.— Kronfeld, M., 'Uber d. biol. Verhaltn. d. Aconitumbliite,' Bot 

 Jahrb., Leipzig, xi, 1889 ; Abstract in Bot. Centralbl., Cassel, xxxvi, 1888, p. 392. 



Protandrous humble-bee flowers. The large sepals are blue, violet, vivid yellow, 

 or brightly mottled, and in conjunction with the smaller petals serve to attract 

 insects. Conspicuousness is enhanced by the aggregation of the flowers into 

 racemes, which usually bear numerous blossoms. The two upper petals are con- 

 verted into long-stalked hood-shaped nectaries, covered by the upper sepal, which 

 is galeate. 



M. Kronfeld describes the stalk of the nectary of Aconitum as a hollow splint, 

 into which nectar-sucking humble-bees insert their proboscis, this being thrust 

 forwards and upwards to reach the actual source of the nectar. 



As Kronfeld points out, the nectary is specialized to a varying extent in different 

 species (see Fig. 1 7). The simplest form occurs in A. heterophyllum Wall., an East 

 Indian form in which there is a tolerably thick stalk, expanding into a cap open 



