The effects of cavity length on nest size, sex ratio and mortality of Centris (Heterocentris) analis (Hymenoptera, Apidae, Centridini)

This study investigated the effects of different cavity lengths in trap-nests on the number of cells constructed per nest, sex ratio and mortality of offspring of Centris analis at three sites in Ribeirão Preto, São Paulo, Brazil. Cavity length did not affect the occupation rates of the trap-nests, with the exception of a preference for the shortest trap-nests found at one site. The number of cells per nest increased with trap-nest length. Cavity length affected neither brood cell size, the arrangement of sexes in the nests, nor the rates of immature mortality from parasitism or other causes, with the exception of one case. Cavity length influenced the sex ratio of offspring, with male-biased sex ratios decreasing as the length of the trap-nest increased. This study showed that an increase in the production of C. analis females can be achieved by increasing trap-nest length.