In recent decades, wild bee abundance and species diversity have declined all over the globe (Winfree, 2010). In temperate climates bees are essential in pollinating wild trees, shrubs and herbs and in the proper functioning of most terrestrial ecosystems (Williams, Corbet, & Osborne, 2015). Most crops require pollination by insects (Kevan, Clark, & Thomas, 1990), so protective measures should be taken at many levels to maintain an adequate level of food production (Losey & Vaughan, 2006, Gruber et al., 2011). Precise recognition of bee ecology is a key to maintaining the stability and species richness of many habitats (Steffan-Dewenter & Schiele, 2004).
Currently, solitary bees are used as pollinators for various crops. Among the species from the Megachilidae family, many have proven to be highly effective pollinators used in agriculture, including the alfalfa leafcutter bee
The wide host plant spectrum of
The aim of the study was to determine the optimal features of the
Red mason bees
The rearing was carried out in 2015 and 2016 in three places: the Medicinal Plant Garden, Wrocław (Poland, Lower Silesia, 51°07′04″N, 17°04′29″E), a housing estate in the Kozanów district, Wrocław (Poland, Lower Silesia, 51°08′10″N, 16°58′42″E) and a garden plot in Kamionki village (Poland, Lower Silesia, 50°40′36″N, 16°32′35″E). In total, for two years of research 5,000 stems of reed were exposed (Medicinal Plant Garden 2,536; Kozanów 1,057; Kamionki 1,407).
The cocoons were winterized and placed next to the nesting material in a cardboard box. In 2015, 1,000 cocoons were placed outdoors, while in 2016 all 3,500 cocoons from the previous year were put out. In September, all occupied reeds were taken from the rearing spots and kept in a refrigerator at a stable temperature of 4°C.
In December, each stalk was cut with a knife on two sides and split. The cocoons were removed from the stalks, and cleaned of excrement, pollen and parasite residue. For each stalk, the length, diameter, vestibulum length (the empty cell at the entrance of the tube) and the contents of every cell were measured. The length of the reed from the inlet to the node was measured using a ruler with an accuracy of 1 mm. To measure the diameter of the inlet, an electronic calliper was used with an accuracy of 0.01 mm. Each parasite-free cocoon was weighed on an electronic scale with an accuracy of 0.001 g. Average mass of cocoons from one nest was used to estimate the correlation between variables. The rate of parasitism for each nest was defined as the number of parasitized larvae in relation to the total number of cells (1 parasitism rate=100% parasitism). The diameter and length of the unoccupied stalks were also measured. Reeds were graded in 50 mm increments (7 ranges: <50 mm, from 50 to 100 mm, from 100 to 150 mm, from 150 to 200 mm, from 200 to 250 mm, from 250 to 300 mm and from 300 to 350 mm) and diameter in 1 mm increments (7 ranges: from 3 to 4 mm, from 4 to 5 mm, from 5 to 6 mm, from 6 to 7 mm, from 7 to 8 mm, from 8 to 9 mm and from 9 to 10 mm). The size of each category was classified according to the percentage of stalks unoccupied compared to the occupied for showing which one range was the most occupied by red mason bee.
The parameters of cell number, vestibulum length, and parasitism rate were analyzed. Values in the text and figures are given as median (Me) with Interquartile Range (Q1 the median of the lower half of the data set; Q3 the median of the upper half of the data set) and mean ± standard deviation unless otherwise stated. In order to show the influence dependence of the diameter and length of stalks on cells number in the reed, cocoon mass, vestibulum length and parasitism rate, the Pearson correlation coefficient was calculated. Linear relations were presented in the drawings. All statistical analyzes were performed in the Statistica v.13.3 program, and the significant level was set to α=0.05.
In total, during the two-year research, 3,293 of 5,000 stalks were occupied. There were 1,777 (54%) reeds without parasites and 529 (15.03%) nests with all parasitized cells. In the all nests, 19,641 cells were counted, in which there were 16,222 cocoons (3,419 larvae in cells were parasitized - 17.4%). The most common insects parasitizing
Red mason bees settled stalks with lengths ranging from 12 to 320 mm (Q1=135 mm, Me=174, Q3=210 mm) (Fig. 1a). The mean length of the occupied reed was 169.45 mm (SD=59.35, n=3,293). The diameter of the reed ranged from 3 to 10 mm (Q1=5.3 mm, Me=5.96 mm, Q3=6.81 mm) (Fig. 1b). The mean diameter of the occupied reed was 6.11 mm (SD=1.12, n=3,293). The mean number of cells in the reed was 5.47 (SD=2.82, n =19,641). A maximum of nineteen cells in the reed were recorded and a minimum of at least one cell (Q1=3, Me=5, Q3=7) (Fig. 1c). The mean mass of the cocoon was 0.085 g (SD=0.029, n=16,222). The cocoon mass ranged between 0.041 and 0.194 g, (Q1=0.06 g, Me=0.078 g, Q3=0.103 g) (Fig. 1d).
The number of cells in the stalks was positively correlated with the length of the reed (r=0.543, p<0.001) and the diameter (r=0.406, p<0.001) (Fig. 2a, b). The mean mass of the cocoon was positively correlated with the length (r=0.362, p<0.001) and the diameter of the reed (r=0.536, p<0.001) (Fig. 3a, b). The mean length of the first cell, the vestibulum, was 38.38 mm (SD=27.19, n=3,293) and the most common range from 70 to 90 mm (Fig. 4a, b). The vestibulum length was positively correlated with the length of the reed (r=0.392, p<0.001) and diameter (r=0.254, p<0.001). The mean rate of parasitism was 0.16 (SD=0.27, n=16,222). The most frequently reported rate of parasitism ranged from 0.2 to 0.3. There was no correlation between rate of parasitism and by the diameter (r=0.108, p<0.001), and the length (r= −0.040, p=0.022). Additionally, no correlation was found between vestibulum length and parasitism rate (r= −0.118, p<0.001).
Red mason bee is a species that relatively easily nests in all available kinds of holes in wood, crevices in buildings, reeds and even plastic pipes (Madras Majewska, Zajdel, & Boczkowska, 2011). This species is easily used in amateur rearing for plants pollination but also in commercial orchards or plantations. The calculations demonstrated that for the effective pollination of apple, cherry and blackcurrant orchards, there is need for, 556, 3,137 and 966 females respectively are needed, or three times more cocoons, because females constitute about 33% of all emerged bees (Biliński & Teper, 2004). In order to optimize the bee rearing, artificial nests of appropriate dimensions and material type should be selected. It is worth considering the nesting material when setting up
Many brood cell parasites enter open cells during its provisioning, when the mother bee is absent. Therefore, females can reduce the risk of open-cell parasitism by limiting the time they are away from the nest (Seidelmann, 2006). The rate of nest parasitization is determined by the diameter of the stalks, so if the diameter of the reed is larger, more parasites can be expected. Also, the size of the red mason bee aggregation may affect the rate of nest parasitization, because at a higher density the parasites did not apear (Holm, 1973), which may be related to the scattering of parasites or the location of nests (Fliszkiewicz, Kuśnierczak, & Szymaś, 2015). A higher rate of parasitism is recorded in hay meadows than in forests or orchards (Fliszkiewicz, Kuśnierczak, & Szymaś, 2015).
The research also demonstrates that the red mason bee preferably occupies reeds if it has a choice of other nesting materials (Wilkaniec & Giejdasz, 2003). However, it reluctantly uses reeds which had already been occupied (Bąk & Wilde, 2003). Therefore, new nesting material should be provided every year, thereby limiting the number of parasitic organisms on
The experiment conducted by us allowed the determination of the optimal parameters of the reed stalks for nesting by the red mason bee