Forces of Flower Visiting Bees

Forces that insects are able to exert to gain access to a food source were measured during visits to a custom-made "artificial flower" for which the insects can be trained (Figure 6.3). The artificial flower consists of a base plate connected to a highly

FIGURE 6.2 (A) S. glutinosa flowers with B. hortorum leaving a flower after a visit; original habitat near Eichstetten. (B) S. sclarea visited by X. violacea (private garden in Schwanau).

FIGURE 6.2 (A) S. glutinosa flowers with B. hortorum leaving a flower after a visit; original habitat near Eichstetten. (B) S. sclarea visited by X. violacea (private garden in Schwanau).

sensitive force transducer (Burster Präzisionsmeßtechnik GmbH, D-76593 Gernsbach, Germany) and a retractable tube behind the posterior wall of the construction. The retractable tube contains a sugar solution (apiinvert, Südzucker AG, D-97195 Ochsenfurt, diluted to 50%) as a food source. The posterior wall is covered by a foam pad with a central hole giving access to the tube with the sugar solution. As the bees are feeding, the thin tube containing the sugar solution is manually retracted. By trying further to reach the food source, the insects start pressing their heads against the foam pad. The induced reactive force is transmitted via the bees' legs and the platform to the force transducer that measures this force with an accuracy of ± 50 ^N. The force transducer converts the forces into a voltage output, which is stored online by a laptop computer. The tested bumblebees were continuously fed with air-dried pollen, and the supply of the colony with sugar solution was interrupted 24 hr before the experiments were started.

TABLE 6.1

Flower Visitors of the Specialized S. sclarea and S. glutinosa, and the Less Specialized S. pratensis

Salvia glutinosa Salvia sclarea

Salvia pratensis

literature

21 51 52

33 55 41/56 X 32 34 57 51 33 X 57 21

50

51 53

54

41/56

57

Bees (Apoidea)

0

Andrena carbonaria

0

Andrena dorsata

+

0

Andrena hattorfiana

+

Andrena labiata

0

Andrena nigripes

0

Anthidium manicatum

0 0 0

+

Anthophora ssp.

[+]

Anthophora fulvitarsis

0

Anthopora quadrimaculate

0

Apis mellifua

N p p +

0

0

n

[0 n]

Bombus ssp.

+

0+

0

Bombus sp.

[0]

+N

Bombus argillaceus

0

Bombus hortorum

+ 0

+ 0 + +

0

0

+

0

Bombus humilis

[0]

Bombus hypnorum

+

Bombus lapidarius

+

0

0

0

Bombus muscorum

0

Bombus pasquorum

+ [0]

0 + +

0

0

+

Bombus pratorum

+

0

n

Bombus ruderarius

+

[0]

Bombus sylvarum

+

0

N

+

Bombus terrestris

+

0

Bombus wurfleini

[N]

[N] [N]

[N]

Eucera ssp.

+

TABLE 6.1 (CONTINUED)

Flower Visitors of the Specialized S. sclarea and S. glutinosa, and the Less Specialized S. pratensis

Salvia glutinosa Salvia sclarea Salvia pratensis literature 21 51 52 33 55 41/56 X 32 34 57 51 33 X 57 21 50 51 53 54 41/56 57

Eucera nigrescens Halictus leucaheneus "Halictus nitidus" Hylaeus sp. Hylaeus communis Lasioglossum sp. Lasioglossum convexiusculum Lasioglossum majus Lasioglossum malachurum Lasioglossum minutissimum Lasioglossum morio Lasioglossum nitidiusculum Lasioglossum pauxillum Lasioglossum pygmaeum Lasioglossum sexstrigatum Lasioglossum xanthopus Megachile sp. Megachile circumcincta "Megachile pyrina (fasciata)" Megachile parietina Osmia aurulenta Osmia bicolor Osmia bicornis Osmia caerulescens Osmia pilicornis Osmia uncinata pn p

CTQ a

Xylocopa itis Xylocopa violacea

Hoverflies

Butterflies

Vanessa cardui Euphydryas aurinia Mellicta parthenoides Lasiommata petropolitana Whites and Yellows (Pieridae) Anthocharis cardamines Aporia crataegi Colias hyale Pieris brassicae Pieris rapae Moths

Siona lineata Plusia gamma Hemaris sp.

Macroglossum stellatarum Hyles euphorbiae

Source: Data was obtained either from the literature (21,32-34,41,50-57) or from this paper's authors, represented by X. Activity by the flower visitors was evaluated by the respective authors or was based on descriptions from the references: + pollinator; 0 visitor (or no details given); N nectar robber; n nectar thief; p pollen thief; [ ] the original author used a synonym.

FIGURE 6.3 Schematic drawing of the artificial flower, a custom-made device for measuring forces exerted by insects to gain access to a food source (for description, see the text). (a) force transducer, (b) base plate, (c) sugar solution, (d) retractable food source, and (e) foam pad.

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