New insights into the diversity of Diptera and the fauna of hoverflies (Syrphidae) in the Seychelles

Two research trips to the Seychelles were conducted in October/November 2017 and January/February 2018. During the two
periods, 50 sites on the islands of La Digue, Mahé, Praslin and Silhouette were sampled using five trapping methods on a total
of 25 collection days. The total Diptera yield consists of 11,200 specimens belonging to 45 families. Among them are only four
hoverfly imagines belonging to three species. Ischiodon aegyptius (Wiedemann, 1830) and Ornidia obesa (Fabricius, 1775)
were found again in the Seychelles, on Mahé and La Digue respectively. On the other hand, Syritta austeni Bezzi, 1915 was
recorded for the first time in the Seychelles, collected on Mahé. For all three syrphid species, the detailed collection data and
the currently known Afrotropical distribution are given. Finally, the results of the dipterological inventory from Justin Gerlach’s
IOBA project (2000–2005) were compared at the family level with those from our study (2017–2018). The diversity of Diptera
in the Seychelles in general and hoverflies in particular is discussed, as well as the influence of various factors on the trapping
results obtained and the resulting assessment of species diversity.