Ropalidiafasciata (Hymenoptera: Vespidae), in Okinawa in Relation to Island Environmental Conditions

The tropical paper wasp, Ropalidia (Icariola) fasciata (F.), nests on leaves of gramineous plants (Miscanthus sinensis Andus. and sugarcane) in Okinawa, where there are frequent, strong typhoons. In Taiwan and Java, where the effects of typhoons are less severe, most nests are on tree twigs. A similar difference is seen in nests of Ropalidia (I) marginata (Lepeletier) in the Northern Mariana Islands and in India. Okinawan R. fasciata also exhibits quite flexible social behavior, low frequency of intranidal dominance behavior, construction of satellite and multiple-comb nests, absconding swarming, and initiation and development of nests in late autumn. Study of the divergence of social habits in eusocial wasps on Pacific Islands will enhance our understanding of social evolution in insects. THE SUBFAMILY POLISTINAE of the family Vespidae occupies a unique position in the evolution of insect eusociality, because this group has both primitively eusocial (without distinct queen-worker polymorphism) and highly eusocial (with distinct polymorphism) species. The latter are characterized by a social system with multiple queens (that is, they are "permanently polygynous" [Jeanne 1991)). This polygynous social structure is remarkably different from that of honey bees, stingless bees, and hornets (except for a few tropical species [Matsuura and Yamane 1990)), in which each colony has a single queen (Wilson 1971). There is a debate about the evolution of such multi-queen social systems, which might reduce relatedness among nestmates (Jeanne 1991, Spradbery 1991, Ito 1993a,b). Thus, the role of kin selection (Hamilton 1964) in evolution of eusociality might be limited. West-Eberhard (1978) proposed the polygynous family hypothesis, which states that polygynous colonies of these polistine genera could have evolved from polygynous, primiI Manuscript accepted 27 April 1994. 2University of Okinawa, 555 Kokuba, Naha City, Okinawa, Japan 902. tively eusocial groups without passing through a monogynous stage. On the other hand, Carpenter (1991) postulated that short-term monogyny among multiple foundresses is the primitive state in the Polistinae, and single-queen and multiqueen social systems are both derived separately from this ground plan. Carpenter's argument was based on the fact that initial polygyny (multi-female founding of new nests) of primitively eusocial Polistes (e.g., Pardi 1942, 1946, West-Eberhard 1969), Mischocyttarus (Jeanne 1972), and Ropalidia (Gadagkar and Joshi 1983) changed to functional monogyny through dominance behavior, where only the top-ranked females could leave reproductive progeny. Carpenter defined this as "short-term monogyny." If primitively eusocial species are found in which many colonies retain multiple egg-layers, the possibility of evolution of multiqueen systems from such species, and the polygynous family hypothesis, will have more support than at present. Ropalidiafasciata IN JAVA AND OKINAWA The genus Ropalidia is a useful subject to investigate the evolutionary process in euso-