Holarctic Chironomus

Species 5f. C. (Lobochironomus) montuosus.

Egan and Ferrington (2015) reported C. (Lobochironomus) montuosus from Yosimite National Park on the basis of pupal exuviae, but the correct locality is coastal rock pools in Isle Royale National Park, Michigan, which may mimic the alpine conditions from which it is reported in Europe.
There is currently no independent confirmation for the existence of C. montuosus in the Nearctic. If confirmed, this species is of Holarctic distribution.

Adults: No adults are known from the Nearctic.

>Male: Based on Palearctic material, the ground color is dark, with the thoracic segments uniform deep black and the abdominal segments dark brown, the rear edge of segment VII brightly colored. The femur and tibia are dark brown, clearly darker than the tarsal segments. Wing with crossvein darkened.
About 13 setae in a clear patch on tergite IX. Superior volsella with a hooked end; Inferior volsella a little stretched and slightly bent. Gonostylus reduces to be very narrow over posterior third.

The female is also very dark, with the genitalia very similar to those of the subgenus Chironomus.

Pupa: (from 2 exuviae collected by Alex Egan - data and photos used with his permission). These pupae fit the Langton description. Length abt. 8 mm. General brown color except for intersegments and anterior anal lobe, marbling of tergite armament laterally, dense small granulation on thorax, small lateral seta at conjunctive IV/V; rims of tergites II-VI rather heavily pigmented; PsB conspicuous.
Cephalic tubercles about 1.3 times longer than wide. Hook row medially broken, 32-33 hooks with a 25µm gap. Postero-lateral spur of segment VIII with 2 dark teeth.
About 80 taeniae on the anal lobe.

a. Cephalic tubercles; b. hook row with medial break; c. lateral tergite coloration; d. pupal spur.

Fourth instar larva: Not known from North America.
Based on Palearctic material, the larva should be a plumosus-type with relatively short PLT (<150 µm). Head capsule pale.
16-25 teeth in the PE. Antennal segment 1 about 104 µm and segment 2 about 34 µm., i.e. A2/A1 about 0.33.

Cytology: 4 polytene chromosomes with the thummi-cytocomplex arm combination AB, CD, EF, G. Nucleolus subterminal in the very short arm G; a BR just near the middle of the arm - further from the end than in the other described Lobochironomus species.
Only a few bands can be identified on the Keyl-system. A large puff, or a BR according to Ryser et al., perhaps group 7, is just distal of the middle of arm B1, with a group of dark bands (perhaps group 8) distally.
The only recorded polymorphism in the Palearctic material is a simple inversion of about the central third of arm B, with one break just distal to the puff, moving it much closer to the centromere, now with two groups of dark bands immediately proximal to it in sequence B2 (below).

(modified from Ryser et al., 1985)

Found: Michigan - Isle Royale National Park (abt. 48.10°N, 88.50°W).

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