Bibio Geoffrey, 1762

Genus Bibio Geoffrey, 1762 View in CoL

SPECIMENS: Both specimens, UAF-GS6, 7 ( figs. 7 View Fig , 8 View Fig ), are well preserved, with intact venation, and the dark, fuscous membrane of the wing preserved. The very dark, heavily sclerotized stigma at the apex of vein R 1 was apparently not preserved (probably retained on the obverse of each specimen, which was not available). However, even the gradation in fuscous coloration is preserved (best in specimen UAF-GS7), being darkest on the costal third of the wing. Specimen UAF-GS6 has the membrane finely crenulate, which may be just preservational. The wings are 5.5 and 6.0 mm long.

DISCUSSION: The latest revision of the extant North American bibionids was by Hardy (1945), in which he included 51 species of the genus Bibio ; he later mentioned ( Hardy, 1981) that there were 53 Nearctic species. There are an approximately equal number of Palearctic species. There are at least a dozen species of Bibio whose distributions extend into Canada (generally to Alberta and Manitoba), and Hardy recorded four species of Bibio from Alaska: B. fumipennis Walker , B. inaequalis Loew , B. labradorensis Johnson , and B. tenellus Hardy. Wing venation rarely distinguishes species in this genus, and the fossil wings are very similar to living species with one possible exception: the base of vein CuA 2 appears separate from the base of CuA 1, instead of being connected by a fork at about midlength. Since a small knob on CuA 1 occurs where the fork would normally occur, it is almost certain that this venational difference is merely preservational. Thus, the Bibio fossils indicate that the present distribution of the genus in Alaska extended at least to the Late Miocene.

Bibionids are an ancient group, with definitive fossils first occurring in the Cretaceous (a Triassic record is incorrect). Nearly 350 names have been attributed to Tertiary bibionids of the Northern Hemisphere (summarized by Evenhuis, 1994). There are nearly 130 species names of Tertiary Bibio alone, from the Pliocene through Eocene of the Northern Hemisphere. Eleven North American fossil Bibio are reported, all except two from the Oligocene of Florissant; the other two are from the Miocene Latah Formation of Idaho ( Lewis, 1969; Lewis et al., 1990a, b). Fitzgerald (1999) described and redescribed several additional Tertiary bibionids, although none are Bibio .

Family Lonchaeidae Rondani, 1856