Species 5m. Chironomus vancouveri Michailova and Fischer, 1986a.

Adult:

Pupa: Not described.

Larva:  About 23-25 mm. long; ventral tubules essentially same length; lateral projections present. Mentum with c1 and c2 teeth well separated (type IIA); fourth laterals do not appear to be reduced (type I).  Aperture of clypeus shorter but wider than that of C. plumosus – about twice as long as wide in C. vancouveri compared to 3.8-5.5 times longer in C. plumosus.
Antenna with RO about the middle of A1.  Mandible with all inner teeth dark (type IIIC).

Cytology:  Four polytene chromosomes with the thummi arm combination AB, CD, EF, G, as C. plumosus.  Nucleolus essentially terminal in arm G, with a BR near the other end of the arm.
Major banding sequences appear the same as those found in Nearctic C. plumosus, but the major differences come in incomplete pairing of similar sequences in hybrids with Nearctic C. plumosus (Michailova & Fischer 1986a & b) and quite different C-banding patterns: C. plumosus has C-banding only at the centromeres while C. vancouveri has numerous C-banded sites along the length of the chromosomes (Michailova 1994, 2014) but the centromeres are thinner.
vanA1:   1 - 2c, 10 - 12a, 13ba, 4a-c, 2g-d, 9 - 4d, 2h - 3, 12cb, 13c - 14, 15b - 19            i.e. as h'pluA2
vanB1:   not mapped on the Devai et al. system.                                                                  i.e. as h'pluB1
vanC1:   1 - 2c, 6c-f, 7a-d, 16 - 17a, 6hg, 11d - 15, 8 - 11c, 6b - 2d, 17b - 22                     i.e. as h'pluC2
vanD1:   1 - 3g, 10b-e, 4 - 7, 18a-d, 8 - 10a, 13a - 11, 13b - 17, 18e - 24                            i.e. as h'pluD2
vanE1:   1 - 3e, 10b - 3f, 10c - 13                                                                                         i.e. as h'pluE2
vanF1:   1a-d, 6 - 1e, 7 - 10, 18ed, 17 - 11, 18a-c, 10dc, 19 - 23                                          i.e. as h'pluF1
vanG1:   essentially as h'pluG1, closely paired, distal bands often unclear.

Although the sequences in C. vancouveri are similar to sequences in Nearctic C. plumosus, the latter have high frequencies of n'pluA9, which has not been found in C. vancouveri.  However, h'pluA2 is common in some Nearctic populations of C. plumosus, so it is possible that this is a situation similar to that of the species pair C. riparius and C. piger, although the appearance of the bands is not as markedly different, being generally thinner bands including the centromere in C. vancouveri.=.

In addition to the cytological studies of the hybrids, Michailova & Fischer (1986b) note that hybrids between C. vancouveri and Nearctic C. plumosus develop at about 90% of the rate of intra-form crosses.
Some differences exist between larval characters of C. vancouveri and those of C. plumosus,notably in the relative lengths of the antennal segments, that of C. vancouveri being more similar to that of C. entis,but differing from both in that segments 3 and 5 are about the same length.

These data raise questions as to the status of C. vancouveri.  Kiknadze et al. (2016) consider it a highly divergent Nearctic population of C. plumosus, but this is on the basis that the Palearctic and Nearctic populations of that species are considered a single species.  The differences in pairing of hybrids and the significantly different C-banding patterns indicate that C. vancouveri must have had some degree of isolation, and presumably for a significant period of time, from C. plumosus, so that the accumulation of heterochromatic regions could evolve.
It is unfortunate that the natural distribution of C. vancouveri is not known and that no further specimens have been found near Vancouver, raising the possibility that this sample was the result of a chance migration from a source population of unknown location.  The status of Vancouver as an international air- and sea-port offers the opportunity for such migration from numerous regions.
The finding of other populations could help clarify the status of this 'species'.

Found: British Columbia - Deer Lake (49.24°N, 122.98°W), Burnaby, Vancouver.