Wild olive seed weevil in South Africa, Anchonocranus oleae Marshall (Coleoptera: Curculionidae), a rediscovery after a century

Abstract

The wild olive seed weevil, Anchonocranus oleae Marshall, 1912 was not found after its description and the study of its biology by Silvestri in 1915. Recently, A. oleae larvae were found alive inside the kernels of wild olives (O. europaea subsp. cuspidata) collected from trees between 2009 and 2012 in the Western Cape, South Africa. No weevil larvae were found in cultivated olives collected during the same period. Only two adult weevils emerged from olives collected on the tree and on the ground. Over the sampling period 20 adults were collected directly on wild olive trees at different sites in the Western Cape and one in the Eastern Cape. All adults were shown to be conspecific with the holotype of A. oleae preserved in the Natural History Museum, London. Females and males have fully developed metathoracic wings, although they were never seen flying in limited field and laboratory observations. Adults in the laboratory immediately fed on wild olive pulp, but refused to feed on cultivated olives, even in the absence of alternative food. Oviposition sites remain visible even when the fruit pulp has dried out. The extremely low rate of adult emergence from wild olives can explain its absence in records of recent surveys. Barcoding COI sequences of young and mature larvae matched reference sequences obtained from A. oleae adults. The clear preference of A. oleae for wild olive fruit and its extremely low occurrence in cultivated olives suggest its possible use in classical biological control programs for invasive wild olive.