Honey bees, Apis species, obtain carbohydrates from nectar and honeydew. These
resources are ripened into honey in wax cells that are capped for long-term storage. These
stores are used to overcome dearth periods when foraging is not possible. Despite the economic
and ecological importance of honey, little is known about the processes of its production
by workers. Here, we monitored the usage of storage cells and the ripening process of
honey in free-flying A. mellifera colonies. We provided the colonies with solutions of different
sugar concentrations to reflect the natural influx of nectar with varying quality. Since the
amount of carbohydrates in a solution affects its density, we used computer tomography to
measure the sugar concentration of cell content over time. The data show the occurrence of
two cohorts of cells with different provisioning and ripening dynamics. The relocation of the
content of many cells before final storage was part of the ripening process, because sugar
concentration of the content removed was lower than that of content deposited. The results
confirm the mixing of solutions of different concentrations in cells and show that honey is an
inhomogeneous matrix. The last stage of ripening occurred when cell capping had already
started, indicating a race against water absorption. The storage and ripening processes as
well as resource use were context dependent because their dynamics changed with sugar
concentration of the food. Our results support hypotheses regarding honey production proposed
in earlier studies and provide new insights into the mechanisms involved.
S1 Fig. Test comb appearance in colony 2. Scans were performed at A) day 1, B) day 2, C) day
5, D) day 8, E) day 12 after feeding. Cell density patterns observed on each day are depicted by icons on the right side of each picture. Note 1) the increasing density and number of filled cells;
2) the changing shape of the area of nectar containing cells due to the relocation of cell content
after workers cleared cells for brood rearing (empty central area in D and E); such changes (1
and 2) also occurred in the other two colonies but with a lower frequency; 3) the dense areas of
cell content neighbouring empty cells.
S2 Fig. Sugar concentration (left y-axis) and filling level (right y-axis) over time in ten individual
cells per colony. Each row corresponds to a colony and shows a representative subsample
of filling and ripening dynamics. The first five cells of each line represent early provisioned
cells that contained solutions already at day 1 (some were relocated at a later stage); the following
5 cells represent eventually capped cells.
S1 Table. Results of Wilcoxon test comparing the filling and content concentration of early
provisioned and eventually capped cells at each scan day. Significant P—values (< 0.025)
after Bonferroni correction are indicated with .
S2 Table. Comparison of cell filling level and content concentration between consecutive
days in early provisioned and eventually capped cells. Significant P—values (< 0.05) from
the robust-ranked method (nparLD) are indicated with .
S3 Table. Results from the two-sample tests for equality of proportions between consecutive
days. The test was performed for each pattern category and for the three colonies separately.
Decrease or increase of proportions between the two days are indicated with < and >,
respectively. Significant P—values (< 0.05) are indicated with .
S4 Table. Results of the Poisson models (log-link in glm(), R) applied for pairwise comparisons
of total number of cells filled between consecutive days in each colony. Decreasing and
increasing values are indicated with < and >, respectively. Significant P-values (< 0.05) are
indicated with .
S5 Table. Wilcoxon-Mann-Whitney test comparing the amount of solution stored in the
three colonies between consecutive days.