Freshwater Macroinvertebrates in Hong Kong

Ephemera spilosa

General appearance
Body size large up to 20mm long (excluding antennae & cerci)
Body cylinderical & elongated (abdominal VII-IX greatly extended); ivory yellow body with purplish feathery gills

Head
* Frontal process concave anteriorly to bifurcate & its length subequal/shorter than width
* Mandibular tusks symmetrical or right tusk slightly shorter than left tusk
Details for mouthparts illustrated in the following pictures

Thorax
Legs fossorial for digging a burrow
Details for each leg illustrated in the following pictures

Abdomen
7 pairs of abdominal gills arising dorsally: gill I bi-lamellae simple & slender, gills II-VII bi-lamellae feathery
Cerci length about half of body length, fringed with dense hairy setae

Legs

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

Labrum

Maxillae

Mandibles

Labium

Distribution:
Widespread in Hong Kong, specimens are recorded from Tong Ming Tsuen and Pak Ngau Shek (Lam Tsuen River), Ma Po Mei (nr. Lam Kam Road), Chuen Lung, Bride's Pool, Ho Chung (Sai Kung), Tai Po Kau Forest Stream, Mui Tsz Lam (Ma On Shan), Wah Ming (Fanling), Pui O and Sam Tsuen (Lantau Island)

Reference:
Dudgeon, D. (1996) The life history, secondary production and microdistribution of Ephemera spp. (Ephemeroptera: Ephemeridae) in a tropical forest stream. Archiv für Hydrobiologie 135: 473-483.