EUSOCIALITY IN AUSTRALIAN GALL THRIPS

STUDIES of the role of haplodiploidy in the evolution of eusociality have been limited to the Hymenoptera, the only insects known to exhibit both reproductive castes and the haplodiploid genetic system1. Because aculeate Hymenoptera share many other traits that may affect sociality, such as provisioning at nests, powerful flight, mandibulate mouthparts, and stings, it has been difficult to separate the effects of haplodiploidy from other characteristics of this taxonomic group2,3. Here I report the presence of eusociality in a second haplodiploid insect taxon, the order Thysanoptera. Subfertile 'soldier' adults of the Australian gall thrips Oncothrips tepperi Karny and O. habrus Mound defend the gall containing their mother and siblings from invasion and takeover by inquiline thrips species and other insect invaders. Australian gall thrips provide remarkable new opportunities for analysing the causes of the evolution of eusociality.