Extract from The South Australian Naturalist 85(2): 76–84 76 The South Australian Naturalist Vol. 85, No. 2 A NEW SPECIES OF CERDISTUS (INSECTA: DIPTERA: ASILIDAE) FROM MONARTO ZOOLOGICAL PARK, SOUTH AUSTRALIA WITH NOTES ON ITS BEHAVIOUR Robert Lavigne Honorary Research Associate, Entomology Section, South Australian Museum, Adelaide. Email: robert.lavigne@samuseum.sa.gov.au; Hexapoda55@gmail.com Erica McAlister Collections Manager and Senior Curator (Diptera), Natural History Museum, London, UK. Email: e.mcalister@nhm.ac.uk ABSTRACT: A new species of robber fly of the genus Cerdistus Loew, Cerdistus weylandi sp. nov., is described based on both sexes. Brief notes on its behaviour and seasonal occurrence are also presented. KEY WORDS: Diptera, Asilidae, Asilinae, Cerdistus, new species, South Australia. In his catalogue of Asilidae of Australia, Daniels (1989) listed 33 species of Cerdistus (Diptera: Asilidae) recorded as occurring in Australia with their known synonymy. Subsequently, Lavigne (2010; 2011) described two additional species, Cerdistus judyjanei, which is widely distributed in South Australia (SA) and Cerdistus hudsoni, from Western Australia, which may belong to an undescribed genus. A key to South Australian Cerdistus is currently in development which will include these new species; however since observations were made on its behaviour and seasonal distribution in Monarto Zoological Park, SA during the 2004–2005 summer–autumn seasons, it was felt worthwhile to describe the species and present these observations separately. Based on examinations of type specimens of Cerdistus in the Australian Museum (AM) in Sydney, in the Natural History Museum (BMNH) in London, in the Oxford University collection (OUM), and in the Paris Museum of Natural History (MNHM), it was determined that the species herein described is new to Science and may also represent a new genus. [A review of Cerdistus and sibling genera is currently being conducted.] DIAGNOSIS: Grey species; femora black; sternites 1–3 with multiple long white hairs directed downward; upper margin of shiny black epandria expands into long curved inwardly directed digit. DESCRIPTION: Holotype: [SAMA 29-001842] Male: Body length: 15.0 mm (Fig. 1). [Body length: 15.0–17.0 mm, ave. 15.9 mm (n=6).]