Propsilocerus

[Martin Spies]

Standard diagnoses and keys for pupae in Propsilocerus Kieffer  --  e.g., Coffman et al. in Wiederholm (1986), Langton & Visser (2003), Tang et al. (2004 in Aquatic Insects 26/3-4: 265-272)  --  appear to include an error that may hinder species identifications and affect interpretations of phylogenetic relations.

As far as I can tell from specimens in coll. ZSM, 'pedes spurii A' (psA) are present posterolaterally on sternite IV only. Structures reported as psA and as present on other abdominal sternites  --  see, for example, Tang et al. (2004), p. 268, key couplet 4  --  are located on postero-lateral dorsal (paratergite) surfaces, and show no vortex-like arrangement of the spinules, thus have nothing to do with psA.

On the pupa of the type species, P. lacustris Kieffer, paratergites III-VI show such posterior armament, whereas paratergite VII does not. Therefore, species separation may still be possible in principle as given in the key by Tang et al. (2004), as long as one examines the paratergites of the segments mentioned rather than the parasternites.

[townning]

Hi Martin,
I have checked my pupal material of P. akamusi. Vortex is present posterolaterally on parasternite IV only, not paratergite surface. 
The drawing line of Tang et al. (2004) is too thick, it does not show the discrete spines of psA.

[townning]

another picture.

[Martin Spies]

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.

[townning]

hi Martin,
I remembered that i had browsed the Russia immature material of Propsilocerus, mainly larvae. If my memory serves me well, you can contact Dr. Kiknadze, She may have the pupae of P. jacuticus. This genus is very special in sf. Orthocladiinae, Pete suggested to transfer into sf. Prodiamesinae.

[Peter Langton]

We appear to be making a mistake here in the application of a technical term, viz. pedes spurii A (see Langton 1999, CHIRONOMUS 12:15 Pedes spurii).  Pedes spurii A are the patches of enlarged points in the posterolateral corners of the sternites.  The spine patches in the posterior of the paratergites are called 'vortex' in Chironominae and belong to a different armament field.  I have only P. lacustris in my reference collection, but it has pedes spurii A on sternites II-V, but a patch of strong spines on only paratergite IV.  Hopefully this will clear up the confusion.....

[Martin Spies]

Dear Peter and all,

I have re-examined the exuviae of P. lacustris on a Thienemann slide which holds specimens from the rearing that had produced the adults used in the original description by Kieffer. Following this I submit that my previous presentation of morphology and terminology was 100% correct. If there has been any confusion in this topic, it was introduced only recently.

The remaining armament on a given abdominal segment allows me to identify beyond doubt whether I am looking at a dorsal or ventral surface. Consequently, I repeat that on those Thienemann exuviae from the type sample of P. lacustris there are what Peter calls pedes spurii A ventrally on IV and different armament fields on several paratergites.

An indication of where something has gone wrong may be the inexplicable claim that "spine patches in the posterior of the paratergites are called 'vortex' in Chironominae". By all means and on all the many Chironominae exuviae that I have looked at, the 'vortex' is located ventrally on segment IV; see also Langton (1991: p. vii).

Whether one has to, or wishes, to call such a structure a 'vortex' in Chironominae but a 'pes spurius A' in other subfamilies is a matter entirely separate from the above.

To clarify these kinds of issues, it would be very helpful to have small 'workshops', or at least microscope viewing opportunities, at each Chironomidae symposium, so that all those interested may view the same specimen together and come to a collective conclusion. In this spirit, I would be glad to carry the Thienemann slide with P. lacustris exuviae with me to Ceske Budejovice.

[Peter Langton]

Sorry Martin, a slip on my part, the vortex is on the parasternite and that is what I meant to write.....but didn't.  Again, I set out the terminology, now over 25 years old clearly in the CHIRONOMUS article I referred to.  But certainly, let's have a look at the material together. 

[Martin Spies]

New evidence

Baranov, V. (2021) Propsilocerus Kieffer, 1923 shares morphological synapomorphies with Prodiamesinae. CHIRONOMUS J. Chironomidae Res. 34: 6 pp. [publd 19.ix.2021]. [https://www.ntnu.no/ojs/index.php/chironomus/article/view/4100/3753]