Wingspan c. 21mm
S. basistrigilis inhabits deciduous woodland most frequently in the southern half of England, becoming more locally distributed further north.
It is rather similar to S. ambigualis in appearance, and is perhaps best identified by means of genitalia dissection.
Flying in July, the adults can be found resting on tree trunks in the daytime, and at night will come to light.
The larva has only recently been described for the first time (click on ?show detail? for description). It feeds on the moss Mnium hornum growing on deep soil, which is not deeply shaded.
Larva: (description R.J. Heckford and P.H. Sterling)
Full details in Entomologist?s Gazette, 56: 211-215.
Foodplant: Mnium hornum (a moss) on deep soil out of deep shade.
Length: Final instar 15 mm.
Head: Head dark brown to black with very pale yellowish and indistinct adfrontal sutures.
Prothoracic shield: Similar in colour to head, occasionally with an indistinct yellowish white
Thoracic legs: Femur and tibia black, ringed whitish at joints, tarsus translucent blackish brown.
Body: Dark grey becoming paler posteriorly, without the greenish tinge often observed in larvae of S. ambigualis.
Spiracles: Peritremes small, black.
Pinacula: Large, shiny, sclerotized, darker than body colour with an olive tinge, becoming paler posteriorly, with either one or two very small black marks usually towards the centre from each of which arises a short black seta.
Anal plate: Similar in colour to the pinacula on abdominal segment 9, with a variable number of black spots.
Prolegs: Translucent whitish, a black mark within the planta appearing almost square just above the crochets on the outer edge of the planta. Crochets blackish brown.
Pupa: In a strong cocoon covered with humus and moss, but not frass; exuviae not extruded on emergence of the moth.