Abstract
Biosociological studies on the Japanese hornets of the genus Vespa have been carried out by the author since 1957. The present paper deals with the behaviour of post-hibernating female of Vespa species in the pre-nesting stage. The hibernated females depart from their hibernacula during the period from early April to early June in the following order : V. xanthoptera-mandarinia-crabro flavofasciata-analis insularistropica pulchra. Fertilized females spend time in taking their own food, mainly tree sap of Quercus trees, for a short period before searching for nesting sites. On the other hand, unfertilized ones seeking tree sap can be observed until July, but they perish without founding nests. Both intra and interspecifically a distinct linear dominance order is recognized among the females visiting tree sap. Each individual can obtain tree sap according to the order established among them. A positive correlation between the social rank relationships and development of their ovaries, as reported in Polistes wasps, was not definitely confirmed.
