Freshwater Macroinvertebrates in Hong Kong

Baetis tatuensis

General appearance
Body size medium-small, probably up to 6 mm long (excluding antennae & cerci)
Body spindle-shaped, head without a 'rigid' between antennae (found in Labiobaetis & Alainites)

Head
Antennae about 2 times as long as head width
The details for mouthparts illustrated in the following pictures

Thorax
Hindwing pads present
Villiopore present
All of legs similar, with dark brown marking on femora medially and on tibiae & tarsi distally

Abdomen
Gills I - VII, single, poor tracheated
Terga dark brown with pale markings: an impression of an inverted triangular mark on terga IV and a large pale area from posterior half of terga VIII to anterior half of tergum X;
Terga with tiny spinules on posterior margin (not in triangular shaped)
Cerci about 0.6 times body length; medial filament shorter than cerci about 0.7 times in length

Legs

Its mouthparts of labrum, mandibles, maxillae and labium are illustrated as follow (hypopharynx is excluded).

Labrum

Maxillae

Mandibles

Labium

Distribution:
In Hong Kong, specimens are recorded from Shek Mun Kap (Lantau Island), Tai Mong Tsai, Ho Chung, Ko Tong Ha Yeung (Sai Kung), Shing Mun, Lam Tsuen River, Shek Shan Tsuen, Chuen Lung, Tan Shan River, Ma Po Mei Tsuen and Lai Chi Wo.

Habitat: Larvae are found in moderately fast flowing water, associated with leaf-litter in unshaded riffles.

References:
Kang, S.C., H.C. Chang & C.T. Yang (1994) A revision of the genus Baetis in Taiwan (Ephemeroptera, Baetidae). Journal of the Taiwan Museum 47(2): 9-44.