Libanoculex intermedius is not a mosquito (Diptera: Culicidae): It is a chaoborid (Chaoboridae)

Mosquitoes comprise a large and abundant group of extant species, the Culicidae, which occur throughout the world except in the Polar Regions, high mountains and isolated islands.All males and the females of many species feed exclusively on plant liquids.However, the females of most species feed on the blood of living animals, and many of those are the vectors of pathogens that cause various diseases in humans.Adult mosquitoes are slender, long-legged flies that are easily recognized by their long proboscis and the presence of scales on most parts of the body.Fossil mosquitoes are uncommon.Some are known from compression fossils and some are known from amber inclusions.Twenty-eight indisputable fossil mosquitoes have been formally described and named: Gilka et al. (2021) described the twenty-eighth species and provided an informative tabulation of the 27 previously known fossil species.Three of those species are representatives of three extinct genera that existed in the Upper Cretaceous Epoch of the Mesozoic Era.Twenty species of the extant genera Anopheles Meigen, 1818, Culex Linnaeus, 1758, Culiseta Felt, 1904, Coquillettidia Dyar, 1905 and Toxorhynchites Theobald, 1901a, and five species from three extinct genera, are known from the more recent Cenozoic Era.The discovery of the three Cretaceous species confirms the view of Edwards (1923) that the Culicidae probably evolved in the Mesozoic.The oldest fossil mosquitoes, Burmaculex antiquus Borkent & Grimaldi, 2016 (Burmaculicinae) and Priscoculex burmanicus Poinar, Zavortink & Brown, 2019 (Anophelinae) are embedded in Myanmar (Burmese) amber from the mid-Cretaceous (89.3-99.6Mya) 1 and Paleoculicis minutus Poinar, Zavortink, Pike & Johnston, 2000 is embedded in Canadian amber from the Upper Cretaceous, Campanian Age (72.1-83.6Mya).Burmaculex antiquus has the general appearance and body structure of extant mosquito species (and so do the other two oldest fossil species), which includes an elongated labium with enclosed stylet-like mouthparts.The legs of Burmaculex antiquus are covered with scales, but other areas, except for the costa and posterior margin of the wing, apparently lack scales.Priscoculex burmanicus, in addition to bearing a predominance of anopheline characters, e.g. the abdomen without scales, bears some unique features, including antennal flagellomeres with scales and wing veins with both slender scales and setae.Paleoculicis minutus is the next oldest fossil mosquito.Morphological features indicate that Paleoculicis minutus shares a closer affinity with culicine mosquitoes than it does with anopheline mosquitoes, which suggests that this ancestral lineage is younger than the lineage that gave rise to the subfamily Anophelinae.That aside, Priscoculex burmanicus, Anopheles dominicanus Zavortink & Poinar, 2000 and Anopheles?rottensis Statz, 1944 are the only other fossil anopheline mosquitoes.The age of Priscoculex burmanicus is noted above, Anopheles dominicanus is contained in Dominican amber from the Miocene (5.33-23.03Mya) and Anopheles?rottensis is from the Oligocene of Germany (23.03-33.9Mya).From the available fossil evidence, it appears that extant groups of the Culicidae evolved in the Cenozoic.Recently, a new distinctive fossil fly, Libanoculex intermedius Azar, Nel, Huang & Engel, 2023, was described as "the earliest known fossil mosquito" from two adult males embedded in Lebanese amber dated to the Barremian Age (125.0-129.4Mya) of the Lower Cretaceous.At a glance, the fly does not have the general appearance of a mosquito, with striking differences not in agreement with the current diagnosis of the Culicidae.Most notably, the overall construction of the mouthparts is unlike that of all "true" fossil and extant mosquito species.As taxonomists normally do when presented with an unknown organism, I ran Libanoculex intermedius through several identification keys.First, using the key of Carpenter & LaCasse (1955), which includes dixid and chaoborid 1 The ages provided for fossil taxa follow the geological timescale determined by the International Commission on Stratigraphy (ICS).These ages generally differ slightly from those provided with the published descriptions of fossil mosquitoes.

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