Description: The body of this scale worm is 12-25 mm long with a greenish-brown to yellow-brown colouration, usually becoming darker towards the head. Frontal horns are prominent. They usually have a complex pattern of stripes and spots, with the elytra (scales) often bearing a yellow spot. Their underside is pale and iridescent. The elytra shed very easily, which can cause problems when trying to identify. Elytra are well fringed on one edge, with strong spines, and have many tubercles and spines which may form a colour pattern.

Habitat: Under stones or shells, or in kelp holdfasts. Found from the lower shore to shallow sublittoral.

Distribution: Recorded from all around Britain and Ireland.

Similar Species: There are various other scale worms that can be easily confused. Careful inspection of key features (e.g. number of body segments, and elytra etc) and use of a specialist identification guide may be required.

Key Identification Features:

• Well fringed elytra, with strong spines.
• Small worm with green-brown or yellow-brown colouration.
• Elytra often bear a yellow spot.
• Prominent frontal horns.

Distribution Map from NBN: Harmothoe impar at National Biodiversity Network mapping facility, data for UK.

iNaturalist: Harmothoe impar at iNaturalist World Species Observations database.

GBIF data for Harmothoe impar

WoRMS: Harmothoe impar at World Register of Marine Species. Accepted name: Harmothoe impar (Johnston, 1839). AphiaID: 130770.

Classification: Biota; Animalia; Annelida; Polychaeta; Errantia; Phyllodocida; Aphroditiformia; Polynoidae; Polynoinae; Harmothoe