Cochliomyia Townsend

Tantawi, Tarek I. & Sinclair, Bradley J., 2013, An update of the blow flies (Diptera: Calliphoridae) of the Galápagos Islands, and first record of Chrysomya rufifacies (Macquart) from mainland Ecuador, Zootaxa 3750 (3), pp. 237-250 : 241-244

Cochliomyia Townsend

In this study, we consider the secondary screwworm fly Cochliomyia macellaria native (not an introduced species) to the Galápagos Islands because this species was first collected with L. pionia by Darwin in 1835 (James 1966) and it is a member of the native species composition of carrion calliphorids in the Neotropical Region (James 1970; Dear 1985). However, James (1966), Peck et al. (1998) and Causton et al. (2006) have labeled Co. macellaria in their studies as an introduced species.

Chrysomya Robineau-Desvoidy

The hairy maggot blow fly Chrysomya albiceps and the Oriental latrine blow fly Ch. megacephala are introduced species to the Galápagos Islands, which were first collected in the Galápagos in 1989 (Peck et al. 1998, where first record of Ch. albiceps was incorrectly cited as 1985). In the same year or earlier, Olsen et al. (1992) recorded for the first time Ch. megacephala from the Ecuadorian mainland. These two species along with Ch. putoria (Wiedemann, 1830) were introduced from the Old World and first recorded in southern Brazil in 1975–1977 (Guimarães et al. 1978, 1979), and since then have become widespread in South America.

Chrysomya albiceps and Ch. megacephala are well known to breed in carrion (Vasconcelos & Araujo 2012; Moretti & Godoy 2013), and both species are of forensic and medical importance (Zumpt 1965; Greenberg 1971; Guimarães et al. 1983; Smith 1986; Olsen et al. 1993; Mavarez-Cardozo et al. 2005; Ferraz et al. 2011). Because third-instar larvae of Ch. albiceps are facultative predators on larvae of other necrophagous flies (Zumpt 1965; Faria et al. 2004), this behavior may have a negative effect on the native fly species in the Galápagos Islands.

Laboratory studies have shown that Ch. albiceps can dramatically lower the abundance of Co. macellaria and Ch. megacephala in South America (Aguiar-Coelho & Milward-de-Azevedo 1995; Aguiar-Coelho et al. 1995; Rosa et al. 2006). Chrysomya rufifaces (Macquart) , a species which also has the same predatory behaviour as Ch. albiceps , could significantly reduce the populations of Co. macellaria in carrion wherever the two species coexist (Wells & Greenberg 1992a, b). In a major survey of human cases of wound myiasis in Goiás State, Brazil, during February 2005 – August 2006, Fernandes et al. (2009) did not record a single case involving Co. macellaria . They attributed this to the ongoing dramatic decrease in the populations of this native Neotropical species resulting from competition with introduced Old World species, especially Ch. albiceps . Results of a study on the abundance of species of Calliphoridae of public health and forensic importance in the Tinguá Biological Reserve, Nova Iguaçu, R.J., Brazil during March 1995 – February 1996 strongly suggest the displacement of Co. macellaria by Ch. albiceps (Batista-da-Silva et al. 2011).

Because carrion fly communities are primarily structured by competition (Norris 1965; Kneidel 1984; Hanski 1987), future field studies on carrion calliphorids in the Galápagos Islands should explore the biological and ecological interactions between introduced and endemic species (see Hanski (1977) for the Canary Islands and Sinclair (2009) for the Galápagos Islands). It should be borne in mind that small isolated islands are characterized by a lower species richness of carrion flies due to fierce interspecific competition (Hanski 1977). In contrast, a higher species richness can be found on large islands and the mainland, where competition among different fly species may be alleviated mainly by differences in habitats (Lane 1975; Martin-Vega & Baz 2013) and seasonality (Tantawi et al. 1996; Martin-Vega & Baz 2013), thus facilitating coexistence.