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Discrimination of closed shapes by two species of bee, Apis mellifera and Megachile rotundata

Raymond Campan¹ and Miriam Lehrer^2,*

¹ Laboratoire d’Ethologie et Cognition Animale, Université Paul Sabatier, 118 route de Narbonne, F-31062 Toulouse, France and
² Department of Neurobiology, Institute of Zoology, University of Zurich, Winterthurerstrasse 190, CH-8057 Zurich, Switzerland

View larger version (15K): [in a new window]   Fig. 1. (A,B) The experimental arrangements used to train and test the bees. (A) Megachile rotundata. Bees were nesting in holes drilled in the back wall of a wooden box. During training, a shape (termed positive, +ve) was presented on a vertical wall that divided the box into two compartments. To reach the nesting compartment, the bee had to fly though an opening in the centre of the shape. During testing, the positive shape was presented simultaneously with a novel shape, their positions being interchanged at regular intervals. (B) Apis mellifera. At the feeding site, two shapes were presented simultaneously, one rewarding (termed positive, +ve), the other not (negative, –ve). Their positions were interchanged at regular intervals. The tube in the centre of the rewarding shape led to the feeding dish; the other tube was closed. (C) Shapes used to test the bees’ discrimination of edge features were presented as a random-pixel pattern against a similarly patterned background.

View larger version (1K): [in a new window]   Fig. 2. (A–E) Choice frequencies (CFs) in favour of the positive shape (inset in each panel) obtained using solid black shapes presented against a white background. Black columns, Megachile rotundata; hatched columns, Apis mellifera. Asterisks denote the level of significance against random-choice expectation (CF=50 %, dashed lines) (2-tests). ***P<0.001; **P<0.025; *P<0.05. NS, not significant. Numbers above columns denote the total number of choices.

View larger version (16K): [in a new window]   Fig. 3. (A,B) Mean choice frequency (CF) for each shape when it served as positive (abscissa) calculated from the results of all tests against the four other shapes. (A) Apis mellifera; (B) Megachile rotundata. Note the different scales on the ordinates. See text for the results of statistical tests.

View larger version (19K): [in a new window]   Fig. 4. (A,B) Regression analyses to test the correlation between the choice frequencies obtained in the tests and the amount of overlapping areas (see inset on left) contained in the pairs of test shapes. (A) Apis mellifera; (B) Megachile rotundata. P-values denote the significance against zero of the correlation coefficient r.

View larger version (1K): [in a new window]   Fig. 5. (A–E) The same as in Fig. 2, but using patterned shapes placed in front of a patterned background, thus presenting the bees with motion contrast, rather than with luminance contrast. Black columns, Megachile rotundata; hatched columns, Apis mellifera. Asterisks denote the level of significance against random-choice expectation (CF=50 %, dashed lines) (2-tests). ***P<0.001; **P<0.025; *P<0.05. NS, not significance. Numbers above columns denote the total number of choices.

View larger version (1K): [in a new window]   Fig. 6. (A,B) Mean choice frequency (CF) (ordinate) for each positive shape (abscissa) calculated from the results of all tests against the four other shapes (hatched columns). (A) Apis mellifera; (B) Megachile rotundata. Note the different scales on the ordinates. For the sake of comparison, the results of the tests using solid shapes (see Fig. 3) are also shown (black columns).

View larger version (18K): [in a new window]   Fig. 7. (A,B) Regression analyses testing the correlation between the choice frequencies obtained and the overlapping areas contained in the pairs of patterned test shapes. (A) Apis mellifera; (B) Megachile rotundata. P-values denote the significance of the correlation coefficient r against zero.