long-legged fly

Description:

The long-legged flies, make up a large family of true flies with more than 7,000 described species in about 230 genera distributed worldwide. The genus Dolichopus is the most speciose, with some 600 species. They are generally small flies with large, prominent eyes and a metallic cast to their appearance, though considerable variation is observed. Most have long legs, though some do not. The males often have enlarged genitalia which can be useful for species recognition. The adults are predatory on other small animals.

Habitat:

Adults are found predominantly in grassy places and on the leaves of shrubs. The adults occur in a wide range of habitats, near water or in meadows, woodland edges and in gardens. Some groups are confined to wet places including sands on the banks of water bodies (Porphyrops, Tachytrechus, Campsicnemus, Teuchophorus).Truly aquatic species are lacking but many are semi-aquatic in the water margin zone. A small number of species develop on the shores of saline inland bodies of water or the intertidal zone of seashores.Other groups are found on trunks of trees damaged by bark beetles.Adults are often seen in a characteristic predatory posture standing high on their legs on the ground or on vegetation, on tree trunks and on rocks and some species walk about on the water surface. The adults are predators, feeding on small invertebrates including Collembola, aphids,and the larvae of oligochaetes. The species of Dolichopus prefer to prey on the larvae of Culicidae. The larvae also prey on small invertebrates and are found in particular in moist soil, moist sand, in rotting organic matter, below tree bark and in tunnels made by bark beetles (Medetera). Larvae of the genus Thrypticus are phytophagous and live in the stems of reeds and other Monocots near water.

Notes:

Medium sized or minute flies (1mm.-9 mm.) flies with long and slender legs and predominantly greenish metallic lustrous in colour.Other species are dull yellow, brown or black.The frons in both sexes is usually broad. The eyes are contiguous on the frons of males (except Diaphorus where they are close set).The mouthparts are short in most species and have a wide aperture as an adaptation for sucking small prey.In most species ocellar bristles and outer vertical bristles are developed on the head. The face is entire or divided into two sections (epistoma and clypeus). The third antennal segment is the largest and usually bears a long, apical or dorsal arista.The legs are thin and the tibiae, usually have long bristle and in some genera the legs are raptorial.In some species the tibia are modified in the male. The wings are clear or tinged ( in some species partially strongly coloured or marked or with distinct spots.There are three radial veins (R1, R2+3, R4+5).The medial vein M1+2 is simple or (rarely) furcate (Sciopus). The anterior cross-vein is in the basal part of the wing. The posterior basal wing cell and the discoidal wing cell are always fused. The anal cell of the wing is always small. There are two veins branching from crossvein DM-Cu in the direction of the wing margin (the upper one in some cases strongly curving or forked into M1 and M2. The abdomen is elongate-conical or flat. The genitalia of the male are often free on a petiole. Tergite 8 is asymmetrical (on the left side of the epandrium.) Most species of the family have well developed gonopods on the distal margin of the epandrium consisting of two or three lobes. The gonopods may fuse with the epandrium (Hydrophorus, Thrypticus, Argyra) or have a suture (Porphyrops, Xiphandrium, Rhaphium). In a number of genera the surstyli attain significant development(secondary outgrowths of the epandrium) (Hypophyllus,Tachytrechus). Sometimes there are two pairs of surstyli - one proximal and one distal (Tachytrechus). The hypandrium is usually represented by a small sclerite, which is sometimes asymmetrical (Porphyrops, Tachytrechus). Males of many species have highly developed cerci. The phallus is developed to variable extent