Advenathrips inquilinus gen. et sp. n. produces colonies within pre-existing colonies of an undescribed species of Dunatothrips Moulton on Acacia aneura, the widespread mulga trees of central Australia. The Dunatothrips adults construct domiciles by sewing together terminal phyllodes of their Acacia host, and within these domiciles they raise their brood in subsocial colonies. Advenathrips inquilinus enters established Dunatothrips colonies, then lays eggs and raises its brood among those of its host, apparently without disrupting or displacing the host colony. This social parasitic, inquiline behaviour differs from that of previously described kleptoparasitic thrips species that are common in the domiciles of various thrips species on Acacia trees in Australia.