The use of the butterfly transect method for the study of the nocturnal moth Luperina nickerlii leechi Goater (Lepidoptera: Noctuidae) and its possible application to other species

Abstract

Results are presented from a survey of the nocturnal moth Luperina nickerlii leechi Goater using the well-established butterfly transect method adapted for use at night. This subspecies is in the British Red Data Book 1 (Endangered) and is included in the UK list of globally threatened/declining species. It is found only at one site (in Cornwall) where it forms a small closed population, apparently restricted to where its larval foodplant Elytrigia juncea (L.) Nevski grows. Recording at night was achieved by counting resting moths on the first transect pass and flying moths on the return transect. Transect moth counts varied from year to year and were used to provide an annual Index of Abundance. The distribution area where Elytrigia juncea dominated the vegetation within the transect and over the whole site was measured and used by comparison with transect counts to provide an annual Population Index, taken at the peak flight period. Capture/mark/recapture surveys were used to give an estimated total site population on one night. Transect counts were generally too low to provide significant indices of abundance, whereas the annual Population Index provided a more meaningful reflection of annual changes in abundance. The usefulness of this method for assessing populations of other nocturnal moths is considered, both for single species and multiple species recording.