INTRODUCTION The use of Lucilia blowflies for maggot debridement therapy (MDT) has become a topic of great interest in South Africa (Williams et al., 2008; F. Cronje & Du Plessis H.J.C, pers. comm). Lucilia sericata (Meigen, 1826) is the species of choice for MDT (Altincicek & Vilcinskas, 2009; Vilcinskas, 2011), but the misidentifi- cation of Lucilia cuprina (Wiedemann, 1830) and L. seri- cata for use in MDT and how best to supplement MDT colonies has raised the issue of species identification (Williams et al., 2008; Tantawi et al., 2010). Lucilia cuprina has recently been used successfully for MDT (Paul et al., 2009; Tantawi et al., 2010; Kingu et al., 2012) although this species is responsible for sheep-strike that causes losses to the wool and meat industries that amount to millions of dollars worldwide each year (Hep- burn, 1943; Ullyett, 1945; Vogt & Woodburn, 1979; Heath & Bishop, 2006). Different populations of L. seri- cata show different degrees of cuprina-like attraction to sheep (Crombe, 1944; Cragg, 1956), but no clear pattern in this myiasis has been noted. These two species have been suspected of interbreeding and producing fertile hybrids in South Africa (Ullyett, 1945). They have been shown to hybridise under labora- tory conditions and to produce fertile hybrids, although there are no reports of this occurring naturally (Ullyett, 1945). Lucilia cuprina has consistently been found to be paraphyletic relative to L. sericata in studies of several mitochondrial genes (Table 1). If they are interbreeding, this leads to an explanation of the medical and veterinary anomalies noted in the biology of these species. Several authors have suggested that these flies should be classified as three species or that L. cuprina should be classified as two subspecies – Lucilia c. cuprina (Wiede- mann, 1830) and L. c. dorsalis Robineau-Desvoidy, 1830 (Waterhouse & Paramonov, 1950; Norris, 1990; Stevens & Wall, 1996; Stevens et al., 2002; Stevens, 2003; Wallman et al., 2005; Wells et al., 2007; DeBry et al., 2010). Lucilia sericata and L. cuprina are morphologi- cally very similar and the adults are difficult to identify using the available keys based on morphological charac- ters without using the male genitalia, which usually requires destructive sampling (Aubertin, 1933; Smith, 1986; Norris, 1990; Holloway, 1991). However, with some experience, the females can usually be reliably identified using the characteristics described by Holloway (1991a). Molecular methods are useful in confirming the taxo- nomic status of these two species (Williams et al., 2008; Tourle et al., 2009; Tantawi et al., 2010). The use of more than one gene for taxonomic and phylogenetic studies is recommended as using only one gene may not give a true picture of relationships or patterns of gene flow (Sperling et al., 1994; Nelson et al., 2007; Whitworth et al., 2007; Tourle et al., 2009). Analysing both nuclear and mito- chondrial genes simultaneously has highlighted introgres- sion and the difference between gene trees and species trees (Page & Charleston, 1997; Nichols, 2001; Stevens et al., 2002; Stevens, 2003; Whitworth et al., 2007; Tourle et al., 2009; DeBry et al., 2010). The purpose of this study was to test for evidence of hybridisation between these two species, shown by a dif- ference between the gene trees produced from sequence data using nuclear, as opposed to mitochondrial, genes from these flies from different localities around South Africa and from sites in Africa, Europe, Australia, Asia, and North America. MATERIAL AND METHODS Adult flies of both L. sericata and L. cuprina were collected in Britstown, Bloemfontein, Cape Town, Durban, Grahams- town, Nelspruit, and Witbank in South Africa (Fig. 1 insert). Lucilia specimens originating from Welkom and Pretoria were Eur. J. Entomol. 110(2): 187–196, 2013 http://www.eje.cz/pdfs/110/2/187 ISSN 1210-5759 (print), 1802-8829 (online) Ancient and modern hybridization between Lucilia sericata and L. cuprina (Diptera: Calliphoridae) KIRSTIN WILLIAMS 1, 2 and MARTIN H. VILLET 2 1 Durban Natural Science Museum, PO Box 4085, Durban, 4000, South Africa; e-mail: WilliamsK@durban.gov.za 2 Southern African Forensic Entomology Research Laboratory, Department of Zoology and Entomology, Rhodes University, PO Box 94, Grahamstown, 6140, South Africa; e-mail: M.Villet@ru.ac.za Key words. Diptera, Calliphoridae, Lucilia sericata, L. cuprina, hybrids, mDNA, phylogenetic, taxonomy, introgression Abstract. There are important but inconsistent differences in breeding site preference between the blow flies Lucilia sericata (Mei- gen, 1826) and L. cuprina (Wiedemann, 1830) (Diptera: Calliphoridae) that have significance for medical and veterinary science. These inconsistencies might arise from hybridisation. The species are difficult to distinguish using external morphology, although the male genitalia are distinctive and there are reliable molecular markers. Molecular evidence of modern hybridisation, derived from a newly developed nuclear marker, the period (per) gene, is presented here. This has implications for identifications of these species based on mtDNA, and may lead to an explanation of the medical and veterinary anomalies noted in these species. 187