Diagnosis. Small to medium-sized (2.0-10.0 mm) flies resembling mosquitoes. Head without ocelli; antennal pedicel strongly enlarged in male, less so in female; male antennae plumose; mouthparts protruding but much less than in Culicidae. Thorax with few to many setae on scutum but with two pairs of bare stripes. Wings narrow; venation as in Culicidae and with scale-like setae on most veins. Abdomen narrow. Chaoborus eggs oval and white when laid, light to dark brown later; chorion transparent; eggshell canoe-like in shape with dorsal longitudinal slit. Larvae transparent; tracheal trunks expanded into paired hydrostatic air-sacs in thorax and in abdominal segment VII. Head with large eyes; mandibles strong; antenna prehensile (adapted for holding or seizing).Mochlonyx larvae with siphon on abdominal segment VIII. Cephalothorax of pupa with thoracic sausage- or truncheon-shaped horn in Mochlonyx and with spindle-shaped horn with small, slit-like tracheal opening in Chaoborus. Caudal end of pupae with pair of articulated, large, rounded, membranous anal paddles, each with supporting midrib and often (Chaoborus) strong marginal ribs.
Biology. The eggs of most Chaoborus are laid in egg rafts in a jelly-like matrix formed like a floating disc with the eggs arranged in a spiral. The number of eggs per raft in Chaoborus normally varies between 60 and 350, occasionally as few as 9 eggs per raft observed indicating interrupted oviposition. Mochlonyx eggs are deposited singly without any special floating mechanism. Mochlonyx and some Chaoborus hibernate as eggs, while some other Chaoborus hibernate as fourth instar larvae and pupate in spring. Pupation of the winter generation takes place from mid April to early June.
General references. Cook (1981b [general, key to genera]), Klink (1982c [Mochlonyx]), Saether (1997a [general], 1997b [general, key to genera]), Smith (1989 [immature stages]), Wagner (1990b [catalogue]).
References to the local fauna. Cock (1954b), Klink (1982c), Kuper & Verberk (2011), Van Maanen (2007), Van Maanen (2007), De Meijere (1911), Parma (1971).
How to quote this page: Haaren, T. van, & P.L.Th. Beuk, 2001. Family Chaoboridae. In: Beuk, P.L.Th. (Ed.): Checklist of the Diptera of the Netherlands, https://diptera-info.nl/news.php?fam=Chaoboridae (date accessed: 02/01/2025).
NL: 7
B: 5
D: 7
UK: 6
World: 200
CHAOBORIDAE
Chaoborus Lichtenstein, 1800
subg. Chaoborus Lichtenstein, 1800
crystallinus (De Geer, 1776)
N
= plumicornis (Fabricius, 1794)
= fusca (Staeger, 1839)
flavicans (Meigen, 1830)
N; added by Cock (1954b: 143)
obscuripes (Van der Wulp, 1859)
T
= fusca (Staeger, 1839): misident. sensu De Meijere, 1911
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