none. New observations on the biology and host plants of the Australian longicorn beetle, Ceresium seminigrum Aurivillius (Coleoptera: Cerambycidae: Callidiopini) are provided. The known larval host plants in Queensland are Acacia penninervis Sieb. ex DC. and A. leiocalyx (Domin) Pedley (Mimosaceae). A comparison of the host plants of C. seminigrum is made with those of the related Australian and New Guinean Ceresium species. The wasp Xanthocryptus sp. (Hymenoptera: Ichneumonidae) is recorded here for the first time as a parasite of C. seminigrum larvae.