Thank you very much for the information and photos, Hongqu.
The problem I see does not include P. akamusi, as the pupa of this species has been described consistently with psA IV only (e.g., Sæther & Wang 1996 in Ent. scand. 27).
In the same work, Sæther & Wang phrased the corresponding sentence in the diagnosis for all pupae in Propsilocerus a little differently from the references I cited yesterday, saying: "Pedes spurii A well developed and conspicuous on sternite IV, absent or weak on V-VI or VII" (op. cit., p. 444). However, I have not found evidence that psA-like structures are present ventrally on abdominal segments IV, V and VI (i.e., if present on V then also on VI) in any known Propsilocerus pupa.
Sæther (1997 in Acta Zool. Acad. Sci. Hungar. 43/3) described the pupa of P. jacuticus (Zvereva) as having psA on sternites IV and V (but not on VI), and illustrated the structure on segment V in his figure 16. Since I do not have access to any pupa of P. jacuticus, I have asked the person holding the specimens seen by Sæther (1997) to check them for this character.
I do not have a reply yet, but if the description proves correct for sternite V, then that still does not extend to "VI or VII" as diagnosed by Sæther & Wang (1996). In any case, in light of the evidence from P. lacustris, species separations like those in Tang et al. (2004) key couplets 4 and beyond would need to be reworded.