Social Biology of Ropalidia: Investigations into the Origins of Eusociality

The evolution of sterile worker castes found in most social insects presents an obvious challenge to Darwin's theory of natural selection. Highly eusocial insects such as ants and honeybees have morphologically differentiated worker and reproductive castes and may be studied with the aim of understanding how eusociality is maintained by natural selection or why highly eusocial species do not revert to the solitary state. In primitively eusocial species such as many kinds of bees and wasps reproductive and worker castes are morphologically identical and social roles are left flexible to be decided by social interactions ampngst the adults. Such species may therefore be studied with the hope of understanding the forces that promote the origin of eusociality. Independent founding species of the tropical wasp genus Ropalidia provide exceptionally good model systems for such investigations. Female wasps eclosing on nests of R.marginata and R.cyathiformis have the option of leaving their natal nests to found their own single foundress nests or remaining on their natal nests to assume the role of a worker The question then is, why such a large number of females remain on their natal nests after eclosion