Key to the species of the Volucella pellucens species group
1. Legs with apexes of femora, bases of tibiae, and basotarsomeres yellowish brown (Figs. 5F, H); head with upper postocular orbit clearly seen in lateral view (Figs. 2C, F)................................................................................................. inflata (Fabricius)
Legs almost entirely dark brown to black (e.g. Figs. 5B, D); head with upper postocular orbit barely seen in lateral view (e.g. Figs. 1C, F)................................................... 2
2. Abdominal tergite 2 predominantly black with a pair of pale transverse areas, at most 2/3 of tergite length (Figs. 5I, K) .................................................... nigricans Coquillett
Abdominal tergite 2 almost entirely pale except for narrow median longitudinal stripe in yellow brown to dark brown (e.g. Figs. 5A, C) ........................................................ 3
3. Abdominal tergite 2 longer than tergite 3 when measured medially; male basoflagellomere in lateral view slightly constricted in middle (Fig. 1C); male eye contiguity about half as long as frontal triangle (Fig. 1B); female eyes densely pilose (Fig. 1F) .................................................................................................. thompsoni n.sp.
Abdominal tergite 2 slightly but clearly shorter than tergite 3 when measured medially; male basoflagellomere in lateral view transversely elliptic (Fig. 4D); male eye contiguity about as long as frontal triangle (Figs. 4B, C); female eyes bare (Fig. 4G) 4
4. Female scutum posteriorly without distinct brown triangular macula, or occasionally with faint brownish tinge (Figs. 5O, 6A, B) .................. pellucens pellucens (Linnaeus)
Female scutum posteriorly with distinct brown triangular macula (Figs. 5S, 6C, D)..... .................................................................................. pellucens tabanoides Motschulsky