Introduction

The Dolichopodidae or long-legged flies are a very large family with about 7,000 species described so far (Yang et al., 2007). The adults are generally small and measure between 1.8 to 10 mm. The brilliantly metallic green shining Sciapodinae are maybe the best known because they are very common on the leaves of ground-vegetation. Many dolichopodid species are associated with water, but they are smaller and inconspicuous and generally less brilliantly coloured.

All adults and larvae are supposed to be predacious except for one genus, Thrypticus of which the larvae are parasites of plants such as water hyacinth. It is not reported yet on Seychelles. Also remarkable is that the Sciapodinae Ethiosciapus bilobatus is supposed to be responsible for the pollination of the famous Coco-de-mer or double coconut endemic on Seychelles (Gerlach, 2003).

A number of subfamilies such as Medeterinae, Neurigoninae and Sciapodinae are associated with trees and other vegetation. The larvae of Medeterinae live in the burrows of bark beetles and feed on their larvae. Adults can be observed on tree trunks and feed on small insects such as aphids. Neurigoninae are large yellow coloured dolichopodids also resting on tree trunks. The biology of their larvae is unknown, but the adults feed on springtails. Sciapodinae are generally observed on the surface of leaves of scrubs and trees. Their larvae live in the soil.

The other subfamilies are generally associated with damp soils, but none have true aquatic larvae. Most subfamilies are terrestrial, but all subfamilies have some representatives associated with marine habitats. The subfamily Aphrosylinae is strictly marine. It is not reported yet from Seychelles, but we expect the genus Cymatopus since it is known from the coast of Kenya (Grootaert in litt.) and is widespread in the Andaman Sea and all over the West Pacific. Larvae of Cymatopus live in the thin crust of algae and debris on rocks and corals in the intertidal zone and they possess elongated terminal spiracles to breath air at low tide. Certain groups are found on sandy beaches such as Argyrochlamys, a genus within the subfamily Dolichopodinae, that was originally described from Seychelles, and that is associated with burrows of ghost crabs. So are many species of the genus Asyndetus belonging to Diaphorinae. Asyndetus is not reported yet from Seychelles, but is expected since it has a worldwide distribution and is very common on tropical sandy coasts. Some Thinophilus are also found on sandy beaches. Mangroves host even more dolichopodid groups: Dolichopodinae such as Paraclius, Hercostomus, Lichtwardtia, and the subfamilies Rhaphiinae, Sympycninae, Peloropeodinae, and Hydrophorinae all have representatives that are endemic to mangrove (Grootaert, 2006).

Lamb (1922) gives interesting observations on the bionomics of various dolichopodids on Seychelles. He also relates the colour of the species to their habitat. Densely white or grey dusted species such as Argyrochlamys are found on sandy beaches and can stay fully exposed to sunlight. Species with a shining metallic green body are also often found in bright conditions while yellow species are found in dark shaded areas in forests.

Nothing is known yet about the phenology of the species on Seychelles. In humid tropical conditions, i. e. under gallery forest bordering streams, dolichopodids are present throughout the year. However they are most common at the beginning and at the end of the rainy season. Studies to gather data on their occurrence are needed here.

History of the study of Dolichopodidae on Seychelles

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Scratchpads developed and conceived by (alphabetical): Ed Baker, Katherine Bouton Alice Heaton Dimitris Koureas, Laurence Livermore, Dave Roberts, Simon Rycroft, Ben Scott, Vince Smith