Rheocricotopus Thienemann and Harnisch

Namayandeh, Armin & Beresford, David V., 2018, A NEW SPECIES IN THE RHEOCRICOTOPUS (R.) EFFUSUS GROUP FROM CANADA WITH A REVIEW OF THE NEARCTIC SPECIES OF RHEOCRICOTOPUS AND PARAMETRIOCNEMUS (CHIRONOMIDAE: ORTHOCLADIINAE) Abstract, CHIRONOMUS Journal of Chironomidae Research 31, pp. 16-29 : 26-27

Key to the known Nearctic adult male Rheocricotopus Thienemann and Harnisch (Modified from Saether, 1985)

Abbreviations: AnP = Anal Point; CD = Crista Dorsalis; Gc = Gonocoxite; Gs = Gonostyle; HP = Humeral Pit; IVo = Inferior Volsella; SVo = Superior Volsella.

1a. Gs either with prominent preapical triangular CD or it’s bent distally, and CD is more apical. SVo broadly rounded, never with projection. Subgenus Psilocricotopus ..................................................... 2 1b. Gs either without apparent CD or its long, low and rounded distally. SVo with or without caudomedian projection. Subgenus Rheocricotopus ...... 6

2a. HP of thorax small and indistinct. (Saether 1985, fig. 2B). AR<0.7......................................... ....................................... R. (P.) conflusirus Saether

2b. HP of thorax large and distinct.AR> 0.7.......... 3

3a. HP very large, rectangular (Saether 1985, fig. 11B). Gs is not bent upwards distally (Saether 1985, fig. 11D)........... R. (P.) glabricollis (Meigen)

3b. HP moderately large, ovoid or circular, if very large and rectangular then Gs is bent upwards distally.................................................................... 4

4a. Gs with CD tooth-like located apically next to the megaseta ( Lehmann 1969, fig. 1; Pinder 1978, fig. 38c).................. R. (P.) chalybeatus (Edwards)

4b. Gs with triangular preapical CD distinctly separatedfrom megaseta............................................... 5

5a. Gs strongly bent distally ( Saether 1969, fig. 44) Costa not produced................................................. ............................ R. (P.) robacki (Beck and Beck)

5b. Gs not strongly bent (Saether 1985, fig. 4D). Costa moderately produced (Saether, 1985, fig. 4C) .................................. R. (P.) chapmani (Edwards)

6a. SVo with or without caudomedian projection........................................................................ 7

6b. SVo broadly rounded without caudomedian projection.............................................................. 9

7a. SVo triangular without distinct caudomedian projection ( Saether 1971, fig. 8D). IVo distally di- vided into two lobes. ( Saether 1969, fig.47)............. ......................................... R. (R.) pauciseta Saether

7b. SVo with distinct caudomedian projection. IVo simple.................................................................... 8

8a. HP small ( Fig. 2c ). SVo with long finger-like caudomedian projections that meet medially ( Fig. 3b–c )......................... R. (R.) reduncusoides sp. n. *

8b. HP large. SVo conical with short tapered caudomedian projections (Saether 1985, figs. 18b, d & e; Saether and Schnell 1988, figs. 3b & d) .......... R. (R.) effusoides (Walker) , R. (R.) effusus Saether , R. (R.) unidentatus Saether and Schnell †

9a. CD weak to absent. AR = 0.66–0.97. Costa with definite extension ≥ 15 μm.......................... 10

9b. CD present as long distally rounded ridge (Saether 1985, fig.16C). AR ≥ 1.0. Costa extension barely indicated <15 μm (Saether 1985, fig.16B)................... R. (R.) amplicristatus Saether 10a. Gc with inner proximal margin bulges slightly before it meets the IVo that strongly projects medially ( Saether 1969, fig. 43; Makarchenko and Makarchenko 2005, fig. 16). Costal extension ~ 30 μm............................. R. (R.) eminellobus Saether ‡

10b. Gc with inner proximal margin continuing straight where it meets the IVo which ends in a small posteriorly directed lobe. (Saether 1985, fig.15C; Caldwell 1984, fig. 2). Costal extension 15–30 μm............. R. (R.) tuberculatus Caldwell ‡

*Will also key to R. reduncus Saether and Schnell , a Palearctic species. See diagnosis and remarks under R. reduncusoides , and Table 3 to separate the two species.

†Theses three species in the effusus group are difficult to separate. See Table 3 for combination of characters, distinguishing the species in the effusus group.

‡ Adult male of R. eminellobus and R. tuberculatus are very similar. Key above can partially separate the two species. Female, pupa and larva of two species are quite distinguishable.

Figures

Figure 2. Rheocricotopus (R.) reduncusoides sp. n. male. a) head, b) antenna, c) thorax lateral view.

Figure 3. Rheocricotopus (R.) reduncusoides sp. n. male. a) wing, b) hypopygium, arrow indicates the sternapodeme, c) superior volsella caudomedian projection.