179 Lichen Case-bearer Dahlica lichenella
(Linnaeus, 1761)Winged males of Dahlica lichenella occur in Europe, though in Switzerland populations with both sexes are far fewer than those with only the parthenogenetic wingless female form. Only females have been recorded in Britain; in a few places in southern England, Cheshire, southern Scotland and Perthshire, but the species may have been under-recorded because of identification problems, and males might yet be found.
The adult lives a very short time, so the cased larva is more likely to be found on sunny rocks, stone walls, wooden posts and tree trunks. The case, triangular in cross section and tapered at both ends, is covered in granules of sand, lichen and/or algae. The larva grows from 1mm on hatching in May to about 5 mm in late September, overwintering full grown until the following February. The larva pupates in the case, and in March or April the pupa extrudes from the case for the wingless female to emerge and lay her eggs in the vacated case.
Positive identification depends on dissection of the genitalia, or examination of the headplate of the pupal exuviae. Specimens should be taken sparingly as excessive collecting could cause localised eradication of this species with limited dispersal ability. Apparently vacated cases with extruded pupal exuviae may contain over 50 ova.