Chrysomya megacephala, Fabricius

Williams, K. A. & Villet, M. H., 2006, A new and earlier record of Chrysomya megacephala in South Africa, with notes on another exotic species, Calliphora vicina (Diptera: Calliphoridae), African Invertebrates 47, pp. 347-350 : 347-348

Chrysomya megacephala

C. megacephala Fabricius is a forensically and medically important fly ( Tantawi et al. 1996; De Souza & Linhares 1997; Centeno et al. 2002). It has been recorded breeding in human faeces, meat and fish ( Laurence 1981, 1986) and as such, is a vector for diseases. Knowledge of its distribution in South Africa is therefore of great importance if we are to make use of its forensic potential and combat the spread of disease.

A specimen of C. megacephala housed in the Natal Museum was collected by M.E. Irwin in September 1971 in Amanzimtoti, and identified by F.K.E. Zumpt in 1979. This specimen predates the first published record of C. megacephala in South Africa, from specimens recorded in March 1978 at Yzerfontein on the south-west coast ( Prins 1979, 1982; Braack 1991). Prins (1982) stated that the contemporary distribution of C. megacephala was restricted to the Cape Town–Yzerfontein and Durban areas. The reference to Durban presumably alluded to a specimen in the South African Museum that was collected by Prins in 1982 in Durban. L.E.O. Braack subsequently recorded C. megacephala in the Kruger National Park in 1984, and provided evidence that it was a recent arrival in the area ( Braack 1991). A specimen was collected at Hogsback in March 1988 by P.G. Hensberg, and this nuisance fly has since been collected in many parts of the country ( Fig. 1 ). It was, however, not recorded during extensive surveys of Northern Cape, Northwest and Free State provinces in 2003 and 2005 (Villet, Richards and Midgley, unpubl. data).

C. megacephala was recorded in Mauritius in 1962, and its original distribution was apparently south-east Asian and east African ( Pont 1980); this species was introduced to South America via Brazil in the 1970s ( Laurence 1981, 1986). Braack (1991) speculated that the species might have spread to the Kruger National Park from Cape Town, or by entering South Africa from the north or from the east, via the port of Maputo. The Amanzimtoti record raises further possibilities. However, we suggest that such speculation is currently pointless because specimens of two related flies, C. albiceps Wiedemann and C. marginalis Robineau-Desvoidy , can disperse about 2.25 km/day and have been recovered 37.5 km and 63.5 km respectively, from where they were released ( Braack & Retief 1986; Braack & de Vos 1990). At such rates, even if C. megacephala blowflies were active for only half of the year, the species could spread over 3000 km a decade, as it did in South America ( Laurence 1981, 1986). If it arrived in South Africa only in 1971, it would still have had seven years to migrate to Cape Town and 13 years to reach the Kruger National Park. Furthermore, this species has been trapped aboard the research vessel, FRS Algoa, while she was over 200 km offshore (Villet, unpubl. data), and can clearly be transported by such means (cf. Laurence 1981, 1986). Representatives of this species may therefore have disembarked from ships from Mauritius or east Africa at several South African ports.

More recently, records from different parts of the country have shown that C. megacephala has spread to various locations throughout South Africa ( Fig. 1 ). In the 35 years since the first record of this species in South Africa, it has extended its range into Western Cape, KwaZulu-Natal, Eastern Cape and Gauteng provinces ( Fig. 1 ). Although very different in biology, specimens of C. megacephala were misidentified as C. bezziana (e.g. Braack 1991). This may account for its apparent absence from Northern Cape, Free State, North West and Limpopo provinces. Lack of records from these provinces may also be due to inadequate sampling during periods when this fly is active.

Figures

Fig. 1. Distribution of Chrysomya megacephala in southern Africa, with date of first record for each site.