Dominance hierarchy in the primitively eusocial wasp Polistes japonicus was analysed in four colonies for two periods: (1) the first-brood period, when only early emerging workers are present on the nest, and (2) the mixedbrood period, when the first and second (last) broods are present on the nest. The rank in the dominance hierarchy was determined based on a sociogram showing a dominance-subordinance relationship for all pairs of workers. During the first-brood period, older workers were likely to be more dominant (older dominance hierarchy), while the rank of workers was reversed during the mixed-brood period, with younger workers being likely to be more dominant (younger dominance hierarchy). However, the oldest and youngest workers were not always the top-ranked workers in the dominance hierarchy during the first-and mixed-brood periods, respectively, and during the mixed-brood period no younger dominance hierarchy was evident when the first or second brood was analysed separately. Higher ranked workers displayed dominance behaviour more frequently, and the lowest ranked worker hardly displayed dominance behaviour. Most workers displayed dominance behaviours primarily towards the worker ranked immediately below in the dominance hierarchy during the mixed-brood period but not during the first-brood period. The bodies of younger workers were larger for the mixed brood, but not for the first brood in some colonies or the second brood in all colonies. The association between body size and rank in the dominance hierarchy was negative during the first-brood period and positive during the mixed-brood period, with a nearly significant trend also seen even when the analysis was limited to the second brood. To explain the above temporal change from an older dominance hierarchy to a younger dominance hierarchy, we propose the hypothesis that the probability of a worker inheriting the colony increases rapidly with colony development, and consequently younger larger workers attempt to move up the dominance hierarchy in order to produce their own offspring by becoming the superseder late in colony development, rather than working harmoniously so as to boost the overall production of reproductive progeny for a colony, which is the strategy adopted early in colony development.

In order to elucidate the dominant-subordinate relationship between the foundress and workers, five colonies of the paper wasp Polistes japonicus were observed in a netted and covered cage located outdoors. The number of workers in each colony ranged from four to eight. Workers were divided into first and second broods. Abdominal wagging and ovipositing were performed almost exclusively by the foundress throughout colony development. However, an analysis of aggressive encounters indicated that although the foundress hardly received dominance behaviors (aggression) from workers, it lacked either partially or completely the following characteristics of the queen that are usually seen in paper-wasp colonies with independent-founding queens (except in one colony that produced no second brood): the queen being socially dominant over any worker (the queen had more wins than losses in one-on-one dominance contests with any worker), exhibiting the highest frequency of dominance behaviors, and directing dominance behaviors primarily toward the socially most-dominant worker. In particular, during the mixed-brood period (when all first-and second-brood workers were present on the nest) the foundress hardly exhibited dominance behaviors toward socially dominant workers (mainly second brood) but frequently directed dominance behaviors toward socially subordinate workers (mainly first brood). The foundress disappeared in two colonies before the reproductives emerged; in these colonies the socially most-dominant worker inherited the colony and laid many eggs. The frequency of abdominal wagging by these two foundresses decreased during colony development, while it did not in the other colonies. This suggests that abdominal wagging provides information about the vigor of the performer. The superseder was socially dominant over all other workers, but spent little time wagging its abdomen and allowed some workers to lay eggs.

Abstract:Multitude frozen sh were strewed around the Tsunami disaster areas from huge freezing storehouses in the northern Japan on March 11, 2011. ere were outbreaks of blow ies from rotten sh in the following months. We carefully worked out on the control strategy a er investigating rotten sh in the early May from Tanohata-town, Iwate Prefecture, the northernmost study city, to Kesennuma-city, Miyagi Prefecture, the southernmost study city. e larvae of Calliphora nigribarbis were abundant in the early May in the rotten sh, and a few of the adults were found around houses at that time. From the end of May to June, the adults of this species were stormed to the residents. en, Phormia regina and other blow ies were replaced to C. nigribarbis. e pest control operators from all over Japan were requested to spraying heap of rubble and rotten sh from May to September in the Tsunami disaster areas. We selected Etofenprox emulsion according to the e cacy and avian low toxicity as insecticides and Fenitrothion EC as for the rest. Fly population declined in the end of July by the insecticide spraying, replacement of gavages rubble-mountains or dried-up rotten sh. e high susceptibility of the blow ies to the insecticide was found.