Rhoenanthus (Potamanthindus) magnificus Ulmer, 1920

Figures 10B, D, 11B, 12, 14, 15

Materials examined.

5 larvae, Thailand, Chiang Mai province, Chiang Dao, Mae Na, 19°19'13.08"N, 98°53'25.98"E, 742 m, 11.III.2016, B. Boonsoong leg. (ZMKU) ; 8 larvae, Loel province, Nam Thob ranger station, 17°15'36.5"N, 101°34'52.9"E, 338 m, 20.III.2016, B. Boonsoong leg. (ZMKU) ; 1 larva, Nan province, Bo Kluea district, Sapan waterfall, 19°11'25.8"N, 101°11'56.3"E, 800 m, 28.XI.2020, B. Boonsoong leg ; 2 larvae, Nan province, Bo Kluea district, Lamer resort, 19°09'08.8"N, 101°09'17.0"E, 28.XI.2020, S. Kwanboon leg ; 3 larvae, Nan province, Bo Kluea district, Mae Nam Wa stream, 19°16'22.6" N 101°10'48.2" E, 848 m, 26.XI.2019, B. Boonsoong leg ; 7 larvae, Chiang Rai province, Mueang district, Mae Kon stream, 19°51'46.1"N, 99°39'04.7"E, 534 m, 6.III.2021, S. Kwanboon leg ; 2 larvae, Chiang Rai province, Mueang district, Mae Kon stream, Pong Phrabat waterfall, 20°00'41.8"N, 99°48'15.1"E, 470 m, 7.III.2021, S. Kwanboon leg.

Diagnosis.

The larvae of Rhoenanthus magnificus (Fig. 12) can be distinguished from those of other Rhoenanthus (Potamanthindus) species based on the following characteristics: i) large body size (18-21 mm), ii) mandibular tusks arched inward about 33-34° (angle measurement as shown in Fig. 10D), iii) length of the mandibular tusks ca 1.4 × length of head, and iv) length of the foretibiae ca 1.5 × length of the forefemora and about 2.9 × length of the foretarsi (Fig. 11B) (Nguyen and Bae 2004).

Distribution.

Chiang Mai, Chiang Rai, Loei, and Nan provinces.

Remark.

The larva of R. magnificus was originally described by Nguyen and Bae (2004) from material collected in northern and central Vietnam. The species is known from southern China and Vietnam. In the present study, we found this species in streams of several provinces (Fig. 14).