The Life Cycle of the Xylophagous Beetle, Steraspis speciosa (Coleoptera, Buprestidae), Feeding on Acacia Trees in Saudi Arabia

Abstract

The xylophagous beetle, Steraspis speciosa, has infected Acacia forests in Saudi Arabia, causing significant damage and even leading to the death of several trees. In the Ha’il region, in the north of Saudi Arabia, an investigation of 13 study sites shows that the Acacia population is mainly composed of three species: A. gerrardii (90.3%), A. ehrenbergiana (7.5%), and A. raddiana (2.2%) and that 21.7% of this population was infected by S. speciosa. The age of the tree (young, adult, old) and environment habitat (Dam, Wadi, Plateau) effects, and insect life-cycle were studied in the protected Machar National Park. Infection in the park, estimated at 25.4%, mainly affects the oldest trees (20.1%) more than the youngest ones (2.3%), while the driest environments (Plateau, 38.8%) are more vulnerable to infection than humid habitats (Dam, 9.4%). The life cycle of S. speciosa lasts about two years, with four stages to complete metamorphosis: mating and eggs (≈3 months), larvae (≈16 months), pupae (≈3 months), and emergency and adults (≈3 months). The larvae stage with many metamorphic instars was the most harmful for tree and takes the longest. The female beetle lays its eggs on weak stem parts. Steraspis speciosa larvae feed on the stems of Acacia trees, and the instar larvae were gathered under the bark of infected stems, harming most of the phloem and a large portion of the xylem. When combined with a prolonged period of drought, S. speciosa causes the withering of numerous branches and, in extreme cases, kills the entire tree.