35.044 Bryotropha dryadella (Zeller, 1850)

Status and Distribution

Apparently restricted to south-west England (Cornwall and Devon), two areas bordering the Thames estuary east of London (in Essex and Kent) and an old record from the Channel Islands (Jersey). Previous records of Bryotropha basaltinella from these areas have all, on dissection, been found to relate to B. dryadella.

National Status: 

pRDB 2

Bradley & Fletcher no: 

777a
Photo courtesy of UK Moths.
Photographer: R J Heckford
Location: Berry Head, Brixham, Devon

Provisional Map

Maps updated with all data received by February 2018.

    Dissection Group

    Foodplant and Larval Feeding Signs

    Larva have been found amongst Ctenidium molluscum (comb-moss), see plant distribution map, frass having been seen when only this moss was available, Barbula ungiculata (bird's-claw beard-moss), a different Barbula sp., a Bryum sp. and Homalothecium lutescens (yellow feather-moss), and, except the last, often in association with a grass - Heckford and Sterling, 2002.

    The larva feed in semi-transparent whitish silken tubes, about two to three times the length of the larvae, which did not have fragments of moss or grass attached and were comparatively sturdy. At a site with Barbula each larva was in a tube spun to the base of a grass (probably a Poa sp.), larvae only being found where the lower leaves of the grass touched the surface of the moss - signs of feeding on the grass blades were found but not definitely associated with B. dryadella feeding. Here, in deeper moss, the tubes were vertical and did not reach the surface; in shallower moss the tube would bend and be almost paralell to the surface.  It appears likely that the larva develops slowly throughout the winter until late March or early April.

    Foodplant Map

    Habitat

    Coastal limestone cliffs, coastal serpentine, extensive sand dune systems, chalk quarries and an old stone wall, where mosses grow in extensive patches, on sand, soil or rocks.

    Finding the Moth

    Larva: in semi-transparent whitish silken tubes about two to three times the length of the larvae, without fragments of moss or grass attached - comparatively sturdy. For more detail see under 'Feeding' on this site.

    Adult: flies in the evening and during the night, when it will come to light.

    Similar Species

    British specimens are very similar to Bryotropha basaltinella.

    In western Europe, on occasions when the two species can be directly and closely examined together, B. basaltinella is slightly more vivid with more contrasting markings and a slightly speckled appearance, whereas B. dryadella has a smooth, almost glossy forewing. These contrasts have so far not been obvious in any British specimens.

    The most useful character appears to be that the costal and tornal patches on the forewing in B. dryadella never point outwards.  When these are fused to form a fascia it is straight or slightly inwards-bent in B. dryadella and slightly outwards-bent (rarely straight) in B. basaltinella.  As these differences can be minute it is nearly always necessary to dissect specimens - the female genitalia are readily separable.  The differences are smaller and can be less clear in the males.

    The presence of the first discal spot above the second plical spot only otherwise occurs in B. basaltinella and B. domestica.

    Larval Occurrence

    Larval Occurrence

    Flight Period

    Flight Period

    Single-brooded from late May to late August.

    Earliest: 4th June 1997 (VC1)

    Latest: 18th August 1996 (VC3)