Cavity Length Affects the Occupation of Trap-Nests by Centris analis and Tetrapedia diversipes (Hymenoptera: Apidae)

Abstract

The ideal cavity dimensions for neotropical cavity-nesting bees with the potential to be managed as pollinators have not been getting proper attention. We investigated whether the occupancy of trap-nests by Centris analis Fabricius and Tetrapedia diversipes Klug, and other nesting aspects, are affected by different trap-nest length. The used trap-nests were cardboard tubes 5, 10, 15 and 20 cm in length, and Ø 8 mm. Occupation rates of 10-cm trap-nests by C. analis was higher than that of the 5-cm ones (χ2=11.17, gl=1, p<0.001). On the other hand, there was not difference between the occupation rates of 10 and 15-cm long trap-nests (χ2=0.51, gl=1, p=0.48), and between the ones measuring 15 and 20 cm long (χ2=1.36, gl=1, p=0.24). T. diversipes occupied a smaller number of 5-cm trap-nests than the 10-cm ones (χ2=1.52, gl=1, p=0.22), as well as that the 15-cm ones were more occupied than the 10-cm trap-nests (χ2=4.23, gl=1, p=0.04); moreover, there was not difference between the occupation of 15 and 20-cm trap-nests (χ2=0.28, gl=1, p=0.59). Both species showed higher rates of dead immatures in nests set in the shortest trap-nests, whereas these mortality rates were lower in the longest ones. By taking into consideration that there was not significant difference in many of the assessed parameters in comparison to values recorded for 15 and 20-cm long trap-nests, it seems likely to recommend the adoption of 10-cm long trap-nests for C. analis reproduction in agricultural sites that depend on the pollination service provided by this bees species.