Eristalinus taeniops (Wiedemann, 1818)

Kondo, Takumasa, Rosero, Robert & Gaviria, Jackeline, 2024, Eristalinus taeniops (Wiedemann, 1818) (Diptera: Syrphidae), an exotic flower fly rapidly spreading in South America: A review, Revista Chilena de Entomología (Rev. Chil. Entomol.) 50 (3), pp. 589-599 : 593-595

Eristalinus taeniops (Wiedemann, 1818)

Diagnosis. Adult flies 9-14 mm long, eyes striped, with five to six slender bands, and spotted (small brown puncta) ( Thompson et al. 1999; Smit et al. 2017) ( Figs. 2 A-C). Wings with a characteristic sinuate R4+5 vein ( Miranda et al. 2013); thorax dull, yellowish gray in color; with four indistinct [longitudinal] black stripes; abdominal segments yellow, with dark [horizontal] bands ( Rossi Rotondi et al. 2020), dark bands thickening near mid areas of first two visible segments, almost touching; last segment predominantly dark ( Fig. 2 ). The larva of E. taeniops is a typical rat tail maggot; for a description of the larva see Pérez-Bañón et al. (2003).

Note. Eristaline flies in the New World share a sinuate R 4+5 vein, but E. taeniops can be easily separated from congeneric species by the presence of eyes with distinct fasciae and puncta; all other species of Eristalinus Rondani, 1845 known from the New World lack fascia (a color pattern with broadband) and maculation on the eyes, except for E. aeneus (Scopoli, 1763) , which has punctate eyes but lacks the stripes ( Thompson et al. 1990).

(Cauca, Colombia). Material examined. Eristalinus taeniops (Wiedemann) . Colombia: Cauca, Silvia, Las Delicias, San Fernando, 02°37′N, 76°20′W, 2600 masl, 10.VII.2023, coll. Takumasa Kondo, ex panoja de quinua, Chenopodium quinoa (grano pastoso), 1 specimen, catalogue No. 10049 [CTNI]; same data except: 13.IX.2023, coll. Robert Rosero, ex panoja de quinua, Chenopodium quinoa (grano lechoso), 1 specimen, catalogue No. 10049 [CTNI].

Biology. Hurtado-Asencio (2013) studied the biology of E. taeniops ; the adults of this species are found in both wooded and open areas but are especially frequent in the vicinity of aquatic environments, such as seasonal ponds, rivers, lagoons, coastal swamps, among others. Under laboratory conditions, the complete life cycle of E. taeniops typically ranges from 60 to 110 days, depending on factors such as temperature, humidity, and the type of food provided ( Hurtado-Asencio 2013). This cycle includes both the pre-imaginal stages (egg, larva, and pupa) and the adult stage; the pre-imaginal period usually lasts between 36 and 54 days (larval stage: 23-39 days; pupal stage: 12-15 days) when reared on a medium such as oats, whereas individuals reared on pig slurry exhibit a pre-imaginal period extended to 65 days ( Hurtado-Asencio 2013). Adult flies typically live between 4 and 8 weeks (under laboratory conditions) and feed on nectar and pollen to complete their development and reproduction; once the adult emerges, it takes about 27 days to reach sexual maturity, and the female adult lays 112 eggs in average in their first oviposition ( Hurtado-Asencio 2013). The complete generation in the congeneric species, E. arvorum (Fabricius, 1787) , reared in captivity under a temperature of 25 °C, lasts about 30 days; adults feed on nectar and pollen to complete their development and reproduction and live for about 1 to 2 months; once the adult emerges, it takes about nine days to reach sexual maturity; and the female adult lays 100- 150 eggs at a time ( Cao et al. 2022). The filterfeeding larvae are known as rat-tailed maggots and inhabit small temporary water bodies with decaying plant material and in sewage from farms and factories ( Rossi Rotondi et al. 2020) and are also known to develop on decomposing animal corpses ( Pérez-Bañón et al. 2003). Carpaneto and Vigna Taglianti (1995) reported a case of accidental myiasis that was likely caused by the ingestion of eggs or small larvae present in contaminated agricultural water and the use of manure by the affected person. Species of the genus Eristalinus can be considered beneficial insects since they are known to be good pollinators ( Sonet et al. 2019). Numerous reports have indicated E. taeniops as a good pollinator (e.g., Morales and Köhler 2006; Tshilingalinga et al. 2023). Studies have been carried out on the mass rearing of the closely related species, Eristalis tenax (Linnaeus, 1758) ( Upchurch et al. 2023) , indicating the importance of eristaline hover flies as pollinators, and decomposers of biofactory residues.

The expansion of exotic insect species, or their introduction and spread beyond their native ranges, is influenced by a variety of factors, including the following:

1) Global trade and transportation. Increased global trade and transportation facilitate the movement of insects across borders, either inadvertently through cargo or intentionally for agricultural purposes ( Hulme 2021). The global movement of commodities, including plants, soil, and wood products, can inadvertently introduce exotic insect species to new areas ( Fenn-Moltu et al. 2023).

2) Climate change. Altered temperature and precipitation patterns can create favorable conditions for exotic species to establish and spread in new regions ( Bellard et al. 2012).

3) Habitat disturbance and urbanization. Human activities that disturb natural habitats, such as deforestation and urban development, can create environments that are more hospitable to exotic species ( McKinney 2002).

4) Agricultural practices. The introduction of new crops and agricultural practices can attract or support exotic insect species, which may become pests ( Liebhold and Tobin 2008).

5) Escape from natural enemies. The enemy escape or escape-from-enemy hypothesis ( Elton 1958; Jeffries and Lawton 1984) or Enemy Release Hypothesis (ERH) predicts that an alien species that is introduced to a new region will increase in distribution and abundance due to the reduced impacts from natural enemies ( Roy et al. 2011).

These factors interact in complex ways, often making challenging the management and mitigation of exotic insect species. According to the distribution records of E. taeniops in the New World, the introduction of this exotic syrphid fly into the New World likely occurred through global trade via airports and seaports, e.g., in Florida and in California, there are the Miami and Los Angeles international airports and numerous seaports, respectively. The same pattern is seen in South America, where most records of E. taeniops are clustered around capital cities with international airports and near the coastline, e.g., RÍo de la Plata in Argentina , Porto Alegre and Rio de Janeiro in Brazil. In Colombia, records of its distribution are concentrated in the Andean region, including Bogota, where an international airport may have been the point of entrance of this exotic syrphid fly. However, this hypothesis needs to be tested since records of iNaturalist may tend to be higher near larger cities. Further studies are needed to study aspects of its biology and its interactions (e.g., interspecific competition) with native syrphid flies.

Figures

Figure 2. Eristalinus taeniops (Wiedemann). A. Adult male fly resting on flower. B. Frontal view of a male specimen. C. Frontal view of a female specimen. / Figura 2. Eristalinus taeniops (Wiedemann). A. Mosca adulta macho descansando sobre una flor. B. Vista frontal de un ejemplar macho. C. Vista frontal de un ejemplar hembra. Photos: A. Ramon Evans (California, USA). B and C. Robert Rosero