Prosopistoma sinense

The family comprises a single genus Prosopistoma

General appearance
Body size small up to about 3mm long, its length slightly longer than width by 1.3 times
Protonotum and mesonotum fused to form a semispherical carapace like a beetle

Eyes located dorsally on head
Dark brown transverse marking over median ocellus between antennae
Gills I - VI concealed in respiratory chamber
Three retractile feathery cerci

According to Tong & Dudgeon's paper (Aquatic Insects, 22, pp122-128), Prosopistoma sinense sp. n. can be distinguished from all other known species of Prosopistoma by the following combination of characters of larvae:
(1) colour pattern of the mesonotum with dark brown recessed areas;
(2) antennae 4-segmented;
(3) apex of inner margin of fore tibiae usually with 6-8 pectinate spines;
(4) five long, finely-serrated bristles arising at base of inner canine and outer canine of mandibles with three distinctive apical teeth, progressively larger from outer tooth to inner one.

 

 

Distribution:
In Hong Kong, specimens are recorded from Lam Tsuen River, Ng Tung Chai, Shing Mun Country Park and Tai Po Kau Forest Stream.

Habitat: Larvae are found under stones in moderate to fast current streams.

Reference:
Tong, X. & Dudgeon, D. (2000)  A new species of Prosopistoma from China (Prosopistomatidae: Ephemeroptera).  Aquatic Insects 22: 122-128.

Remark:
The illustrated specimen above is a sole individual in collection, thus it is retained well intact not to undergo dissection. The details for gills and mouthparts have been described in Tong & Dudgeon's paper.