Nepotistic colony fission in dense colony aggregations of an Australian paper wasp.

Social insects are highly diverse in their social structures, aside from the consistent presence of reproductive castes. Among social insects, the Australian paper wasp Ropalidia plebeiana constructs extremely dense colony aggregations consisting of hundreds of colonies within a few square meters; however, little is known about the aggregation structures. We genetically analyzed the colony and population structure of R. plebeiana, and concomitant variations in colony sex ratios. In spring, the foundress (candidate queen) group started their colonies on a single old comb from the previous season, subsequently dividing these old combs via relatedness-based comb-cutting. Female philopatry, a prerequisite condition of Local Resource Competition (LRC), was confirmed. The colony sex ratio of reproductive individuals (male and female offspring for the next generation) became slightly male-biased in larger colonies, as predicted under LRC. However, the number of foundresses was positively associated with the number of reproductive individuals, suggesting that Local Resource Enhancement (LRE) also operates. Although the population structure appears to meet the prerequisites of LRC, the sex ratio appears to be modulated by factors other than LRC. Rather, through LRE, the availability of female helpers at the founding stage is likely to mitigate the sex ratios predicted under LRC.

Eusocial wasp fauna of Sulawesi Island, the central island of Wallacea (Hymenoptera: Vespidae; Polistinae, Vespinae).

Taxonomy of eusocial wasps (Polistinae and Vespinae) occurring in Sulawesi Island, the central island of Wallacea, is reviewed. Sixteen (12 polistine and four vespine) species are recognized. Polistes (Polistella) stigma, known to be widely distributed in southern Asia and Australasia, is newly recorded for Sulawesi Island. A key to the Sulawesian eusocial wasp species is provided. Their biogeographical characteristics are discussed to show that the Sulawesian eusocial wasp fauna is composed of Oriental elements.

Genetic Structure and Potential Environmental Determinants of Local Genetic Diversity in Japanese Honeybees (Apis cerana japonica).

Declines in honeybee populations have been a recent concern. Although causes of the declines remain unclear, environmental factors may be responsible. We focused on the potential environmental determinants of local populations of wild honeybees, Apis cerana japonica, in Japan. This subspecies has little genetic variation in terms of its mitochondrial DNA sequences, and genetic variations at nuclear loci are as yet unknown. We estimated the genetic structure and environmental determinants of local genetic diversity in nuclear microsatellite genotypes of fathers and mothers, inferred from workers collected at 139 sites. The genotypes of fathers and mothers showed weak isolation by distance and negligible genetic structure. The local genetic diversity was high in central Japan, decreasing toward the peripheries, and depended on the climate and land use characteristics of the sites. The local genetic diversity decreased as the annual precipitation increased, and increased as the proportion of urban and paddy field areas increased. Positive effects of natural forest area, which have also been observed in terms of forager abundance in farms, were not detected with respect to the local genetic diversity. The findings suggest that A. cerana japonica forms a single population connected by gene flow in its main distributional range, and that climate and landscape properties potentially affect its local genetic diversity.

Review of the paper wasps of the Parapolybia indica species-group (Hymenoptera: Vespidae, Polistinae) in eastern parts of Asia.

Nine species of the Parapolybia indica species-group in eastern parts of Asia are reviewed. Four new species are described: P. flava sp. nov. (Vietnam), P. crocea sp. nov. (Japan), P. nana sp. nov. (Vietnam), and P. albida sp. nov. (Vietnam). Parapolybia indica (de Saussure, 1854), P. bioculata van der Vecht, 1966 and P. tinctipennis (Cameron, 1900) are redescribed. The status is reinstanted for P. fulvinerva (Cameron, 1900), stat. resurr. and P. tinctipennis (Cameron, 1900), stat. resurr. and new status is proposed for P. bioculata van der Vecht, 1966, stat. nov. Parapolybia tinctipennis (Cameron, 1900) is newly recorded from China, Vietnam and Laos. The key to species is given. The nests of P. indica, P. bioculata, P. tinctipennis, P. flava and P. crocea are remarked.