Social behaviour of two primitively eusocial wasps,Ropalidia sp. nr.variegata andR. gregaria gregaria (Hymenoptera: Vespidae) in the Northern Territory,Australia, with special reference to task specialization and mating inhibition

Social behaviour of females of the Australian paper wasps,Ropalidia sp. nr.variegata (V) andR. gregaria gregaria (G) was observed near Darwin, the Northern Territory, Australia. Both species constructed multiple combs after the emergence of the first progeny. Frequency of intranidal dominance acts in speciesV on the post-emergence nests was significantly higher than that on the pre-emergence nests, while the frequency was constantly high in speciesG throughout the pre- and post- emergence periods. Some females ofG were specialized, at least on single days, to perform the particular task of water collection. In both species the dominant female tended to occupy the largest comb and subordinate females smaller combs. InG, not only the top-ranked female but also low-ranked ones oviposited, and a small proportion of eggs laid by the latter survived at least until the end of observation. InV, each colony had only 1 inseminated female which had highly developed ovaries, suggesting that subordinate females do not mate despite the presence of males. Such a limitation of mating to a single female in a colony has not been described previously in primitively eusocial wasps.