Diamesinae: Tribes and genera

This subfamily comprises the austral tribes Heptagyiini, Lobodiamesini, South African Harrisonini, and the boreal Diamesini and Boreoheptagyiini (Semenchenko et al. 2024). Larvae are lotic, largely cool stenothermic. Boreoheptagyia, Diamesa, Pagastia, Potthastia, Pseudodiamesa, Sasayusurika, Sympotthastia and Syndiamesa all occur in oriental China (Sun et al. 2019) and may be expected at elevation in south-east Asia.

1 Dorsal head capsule tuberculose (Fig. 14A). Parapod claws arranged in circlet (Fig. 14B). Body with multipointed spines (Fig. 14C)................................................. Tribe Boreoheptagyiini ........ Boreoheptagyia Brundin [L. in forest streams, seeps. B. sasai Makarchenko & Endo common oriental China (Fujian). B. alulasetosa Makarchenko, Wu & Wang, B. kurobebrevis (Sasa & Okazawa), B. zhengi Lin & Liu in sw China (Guizhou, Yunnan) (Makarchenko et al. 2008, Lin et al. 2021). B. cf. ambigua & B. rotunda Serra-Tosio near Sino-Burma border; Holarctic]

1’ Head lacks tubercles. Body not spinose. Parapod claws irregular (Fig. 14D)................... Tribe Diamesini ...... 2

2(1) Mentum toothless (Fig. 14E). Premandible with c.15 small, pointed teeth. Mandible lacks seta interna.................................................................................................. Potthastia longimanus gp. [lotic Potthastia cf. longimanus (Kieffer) rare oriental China (Guangdong); Holarctic]

2’ Mentum toothed (Fig. 14F). Premandible with 13 or fewer broader teeth. Mandible with or without seta interna.......... 3

3(2) Median mentum with 3 subequal teeth separated from lateral teeth (Fig. 14F)................ Pseudodiamesa Goetghebuer [P. nivosa Goetghebuer from 3500 m. oriental China, n. Yunnan, e. Tibet, Hengduan Mt.; Holarctic)

3’ Median mentum abutting to narrowly separated from first lateral tooth........................................... 4

4(3) Maxillary palp with setal fan each side (Fig. 14G). Mandible without seta interna. Premandible with 1 tooth............................................................................................ Sasayusurika Makarchenko [2 spp., S. nigatana (Tokunaga), ♂ Zhejiang Province (Sun et al. 2019): Pe oriental China (Fujian and Yunnan., inc. Gaoligong Mt.), e. Palaearctic]

4’ Maxillary palp lacks setal fans. Mandible with seta interna (Fig. 14H). Premandible with 2 + teeth.................... 5

5(4) Mentum evenly curved, with>16 subequal distinct teeth (Fig. 14J). Procercus small or absent; 4 anal setae arise from body wall; if procercus lacking, subapical seta arises anterior to anal setae (Fig. 14I)....................... Diamesa Meigen [D. cranstoni Willassen, e. Malaysia, Sabah, G. Kinabalu, 3200 m., 3 undescribed spp. in montane oriental China (Nanling Mt. and Wuyi Mt.) from 1000–1500 m., Holarctic, montane Afrotropics]

5’ Mentum with fewer teeth (Fig. 14N) or teeth indistinct beneath ventromentum (Fig. 14M). Distinct procercus bears 5–7 anal and 2 subapical setae (Fig. 14K)......................................................................... 6

6(5) Mentum apically truncate with 4–6 ridge-like median projections (Fig. 14M). Setae submenti displaced posteriorly, nearer to postoccipital margin than mentum (Fig. 14M)................................................... Pagastia Oliver [P. lanceolata (Tokunaga), P. tianmumontana Makarchenko & Wang, oriental China (Guangdong), in montane subtropical streams at maximum elevation of 500 m., Pe from 1000–1500 m., oriental China (Yunnan, Fujian); Holarctic]

6’ Mid-mentum rounded, not ridged (Fig. 14L, N). Setae submenti nearer mentum than postocciput..................... 7

7(6) Mid-mentum broad, median tooth dome-shaped. 5–6× width of 1st lateral tooth (Fig. 14L)........... Potthastia gaedii gp. [montane streams, Potthastia cf gaedii, Potthastia montium Edwards, oriental China; Holarctic]

7’ Median tooth of mentum rounded or bi-lobed, <3× width of 1st lateral tooth...................................... 8

8(7) Median mental teeth (sometimes also first laterals) paler than outers (Fig. 14N). Premandible with dominant apical tooth and 2–4 small inner teeth; labral lamellae comprising 2 rounded scales............................... Sympotthastia Pagast [S. takatensis (Tokunaga) Korea, S. wuyiensis Liu, Ferrington & Wang, Jiangxi, transitional oriental and palaearctic China (Liu et al. 2016); Holarctic]

8’ Mental teeth unicoloured (Fig. 14O). Premandible apical tooth no stronger than 1st of 5 distinct inner teeth; labral lamellae comprising 5 well-developed scales (Fig. 14P)............................................... Syndiamesa Kieffer [S. montana Tokunaga, S. yosiii Tokunaga, oriental China; Holarctic]