177 Lesser Lichen Case-bearer Dahlica inconspicuella
(Stainton, 1849)Wingspan (male) 9-13 mm.
Dahlica inconspicuella has been recorded locally, sometimes commonly, in southern England to Lancashire and Yorkshire, and nowhere else in the world. Like the other two British species of Dahlica, the female is wingless, but D. inconspicuella differs in having winged males.
The larva and its case are similar to the other Dahlica species and can be found on sunny rocks, stone walls, tree trunks, fences, or even old roofing felt on a strand line. Positions sheltered from the wind appear to be favoured. The case, triangular in cross section and tapered at both ends, is covered in granules of sand, with variable amounts of lichen and/or algae. It grows from June to March when it is about 6 mm long. After overwintering as a larva, it attaches the anterior of the case by a pad of whitish silk to an upright surface exposed to the sun and pupates in the case. In March or April the pupa extrudes from the posterior (lower end) of the case for the moth to emerge. The wingless female then attracts a male and lays her eggs in the vacated case.
Positive identification of females depends on dissection of the genitalia, or examination of the headplate of the female pupal exuviae. On D. inconspicuella, the antenna sheath and leg sheath are nearly the same length on the female pupa. Males are easily identified by their wings, or by the wing cases and much longer antennal sheaths on the exuviae, as the other two British Dahlica species do not have males. Bankesia conspurcatella also has a case with triangular cross section. It differs in overwintering as a pupa, and the male having a tiny spur on the tibia of the foreleg, and having cilia arranged all round the circumference of at least part of the antenna
In Europe there are sixteen or more Dahlica species, including two-sex forms of the other two British species, which have males with similarly patterned wings.
In the Netherlands, specimens of Dahlica sauteri (Hättenschwiler, 1977) have at times been recorded as D. inconspicuella. The female headplate of D. sauteri is very similar, having the leg sheath a similar length to that of the antenna sheath.