The Production of Males in Queenright Colonies of Trigona (Scaptotrigona) Postica

Workers and males of stingless bees (Meliponini) emerge from morphologically similar cells. Normally only one bee is reared in each brood cell, but in four Trigona postica colonies examined between September and February, 689 out of 2544 brood cells contained more than one egg. In these months the number of males is at a maximum. Nurse bees (workers) even in queenright colonies had developed ovaries and laid two distinct types of eggs: male-producing eggs (1.305 ± 0.033 mm long), and spherical eggs which served as food for the queen. The male eggs were laid in cells in which the queen had already laid, before these were sealed; the male larva survived, killing the other larva within the first 3 days of larval life. In normal queenright colonies the queen usually laid female-producing eggs (1·185 ± 0·018 mm long), but she also sometimes laid male-producing eggs (1·315 ± 0·033 mm long). On three occasions she was seen to lay a second egg in a cell, and these eggs were similar in length to the male-producing eggs. The production of males by the laying workers, which has not previously been described, increases the genetically active population of the colony