EVOLUTION OF INSECT SOCIETIES: SOME INSIGHTS FROM STUDYING TROPICAL WASPS Raghavendra Gadagkar Centre for Ecological Sciences & Centre for Theoretical Studies Indian Institute of Science Bangalore 560 012, India 1. INTRODUCTION With the exception of one species of a sphecid wasp all social wasps belong to the family Vespidae. This family is traditionally divided into three sub-families namely, the Stenogastrinae, the Polistinae and the Vespinae (Richards, 1962; 1978a,b). It is our good fortune that India is blessed with representatives of each of the three sub-families and also each of the three tribes of Polistinae (Gupta and Das, 1977). But it is also a great misfortune that, barring a few scattered reports (Davis, 1966a,b; Gadgil and Mahabal, 1974; Gadagkar, 1980 ; Belavadi and Govindan, 1981 ), there is virtually no information on the Indian fauna of social wasps. Although the Indian groups are in dire need of taxonomic revision, it must be acknowledged that the excellent, if somewhat outdated, works of the Dutch taxonomist, J. Van der Vecht (1941, 1957, 1962, 1966} have rescued those intent on studying the biology of Indian social wasps from despair. Das (1982) has recently attempted a heroic revision of the entire family but taxonomic works are of little value as long as they remain as unpubiished Ph.D. theses. It is in this background that we at the Indian Institute of Science, have initiated a long term study of two species of common social wasps namely Ropalidia marginata and R. cyathiformis. Primitiveiy eusocia! insects such as these are of great topical interest because of the insight they are expected to provide into the forces moulding the evolution of sociality in animals. Tropical species of wasps and bees live in colonies that may be initiated at any time of the year and their colonies may also be perennial, providing opportunities for queen replacements, colony fissions and emigration of potential queens to initiate new colonies. The increased scope for reproductive competition in such situations makes them excellent model systems in insect sociobiology. Tropical wasps have been extensively investigated from this point of view and these studies have also been repeatedly reviewed (West-Eberhard, 1969; Jeanne, 1972, 1980; Litte, 1977, 1979, 1981; Gadagkar, in press). In the limited time available, I shall briefly summarise some aspects of our work at the Indian Institute of Science. Sociallnsects: An Indian Perspective (eds.) G.K. Veeresh, A.R.V. Kumar and T. Shivashankar, Published by IUSSl-lndian Chapter, Bangalore (1990). 129