Coots et al. (2012. Forests 3: 986-996) don't say how they identified their specimens, but it appears from the literature cited that the primary source they used was the monograph by Johannsen, published in 4 parts from 1909 to 1912. The only more recent work on these insects that is cited is the generic key by Vockeroth in the Nearctic Manual (1980), although it appears from the names of the three Phronia species listed that they might have used the 1975 paper on this genus by Gagné, since none of those three names are mentioned by Johannsen.
The other species listed are all included by Johannsen, with exception of Mycomya vulgaris, which was described but not illustrated by Garrett in 1923. The wing figure representing this genus in Vockeroth's work is labelled vulgaris, but it is a typical generic wing so could not be used to identify a species. The genitalia of vulgaris were figured by Elizabeth Fisher in her 1937 thesis and by Edward Coher (1959), so perhaps they saw one of these. However, Väisänen (1984) revised the Holarctic species of Mycomya and found vulgaris to be a synonym of M. simplex (Coquillett), so it was correctly under that name in Johannsen.
They acknowledge in the introduction that more than 700 species of fungus gnats are known in North America. Although Johannsen included less than 370 species, they apparently assumed that their specimens could be accurately identified from his work. In Bolitophila they list 3 species, all among the 4 included by Johannsen. Even by the Nearctic Catalog (1965), 20 species of Bolitophila were known from North America and several more are now known to occur. The chance that all their material of this genus belonged to the species included by Johannsen is extremely remote. Also B. disjuncta has long been known to be a synonym of B. dubia.
They have updated some generic names following Vockeroth, using Leptomorphus, Saigusaia and Orfelia for species included by Johannsen in Diomonus, Boletina and Platyura respectively. However, their use of the name Lasiosoma is puzzling; it was used for this species by Osten Sacken (1878), but Johannsen synonymised it with Sciophila and it hasn' t been used since. They have also followed Vockeroth in including all species in the family Mycetophilidae, although most authors now recognise families Bolitophilidae (for Bolitophila) and Keroplatidae (including Orfelia). Orfelia genualis, the only species of Keroplatidae mentioned in this paper, was transferred to the genus Lyprauta by Neal Evenhuis in the World Catalog of Keroplatidae (2006), but there is no certainty that genualis was the species they found.
The other major work they have missed is that by Laffoon (1956) on the genus Mycetophila. The three species they list are all treated as synonyms by Laffoon, and M. punctata is equivalent to the fungorum group, now known to comprise several species in N America, all separable only by characters of the male genitalia.
It should be apparent from what I have said that all the species identifications in this paper must be regarded as unreliable, and it is fortunate that voucher specimens have been preserved for possible future examination by a competent researcher.
The habitat they studied probably supports hundreds of species of fungus gnats, so only finding 24 species is in itself surprising, although the collecting techniques being unsuitable for this group might account for this. However, since they collected 990 specimens, it is highly likely that they have confused two or more species under many of their names and if they have only preserved a few vouchers this will not be possible to check.
As most of the gnats they found would be developing in fungi on the forest floor (either terrestrial or on dead wood), I'm not sure that the level in the canopy at which they are dispersing is particularly significant, but flight interception traps would have caught a lot more.
While as I have said, more than 700 species are already recorded from N America, there are many species as yet undescribed. The European fauna is better known and includes more than 1200 species, and it is likely that at least as many will be found to occur in the Nearctic. Every generic revision that is published includes previously undescribed species, from which it should be apparent how unsound it is to name specimens from old literature, and without seeking the assistance of a specialist.
P.S. These comments were sent to the editors of the journal, who have brought them to the attention of the authors and have asked them to consider a revision. This may be practicable after the material concerned, which is preserved at the University of Tennessee, has been critically examined.