Gnat common name for any one of a number of small, fragile-looking two-winged flies of the suborder Nematocera, order Diptera. Mouthparts of gnats are always suctorial and frequently adapted for piercing. They are identified from other flies by the presence of relatively long hair-like antennae, and long legs. The antennae are particularly well-developed in males. Male gnats fly in swarms, usually toward evening, dancing up and down a few feet from the ground. The larvae are free living, most feed on plants and are legless; the head-capsule is well-developed, and mouthparts are of biting type.
The gnats which have been reported from Bangladesh are two species of the family Cecidomyiidae, commonly known as gall gnats or gall midges, viz, Lasioptera falcata, larvae are seen in the stem of the bitter gourd, and Pachydiplosis oryzae- larvae make gall on paddy leaf.
Eighteen species under 11 genera of Mycetophilidae, commonly known as fungus gnat are: Allactoneura cincta- larvae feed on fungi, reported from Sylhet; Dilophus gratiosus, larvae feed on decaying wood and fungi, reported from Sylhet; Isoneuromyia annandalei, larvae feed on fungi, reported from Sylhet; Leia arcuata- larvae saprophagous on decaying wood, reported from Mymensingh; Leptomorphus ornatus- larvae feed on fungus, reported from Sylhet; Macrocera ornata- larvae feed on fungus, reported from Dinajpur; Mycomya ferruginae- larvae feed on decaying wood and fungi, reported from Rangpur; Platyura ruficornis- larvae feed on fungus, reported from Sylhet; P. venusta- mycophagous, reported from Chittagong; Pleciomyia melanaspis- saprophagous, reported from Rangpur; Rhymosia annulicornis- mycophagous, reported from Mymensingh; R. humeralis- fungus feeder, reported from Sylhet; Sciara diversipes- saprophagous, reported from Dinajpur; S. fluvescens- fungus feeder, reported from Rajshahi; S. inconspicua- larvae feed on decaying vegetable matters, occurs more or less in all districts of Bangladesh; S. orientalis- larvae feed on fungi, reported from Dinajpur; and S. rufithorax- larvae feed on vegetable matters, reported from Rajshahi. The term 'gnats' is also applied to the less virulent mosquitoes and Phantom gnats (family Culicidae). [Humayun Reza Khan]