Attraction to light - from how far do moths (Lepidoptera) return to weak artificial sources of light?

Moths are frequently used as indicators of biodiversity or habitat quality. Light traps are the most effective and widely used method for gathering data on moth communities. Knowing the distance from which moths are drawn to a light trap is therefore essential for the ecological interpretation of such data. Two community-wide mark-release-recapture experiments were carried out in forest habitats in central Europe in order to investigate whether the percentage of marked moths recaptured at weak artificial light sources (2 x 15 W UV-light tubes) is dependent on the distance they were released from the light source. Altogether 2,331 moths belonging to 167 species were caught at light traps and released at distances of 2-100 m. Of these moths 313 returned to the light trap within 5 min of release. Percentage recapture was generally low (gross rate 13.4%) and strongly decreased with increase in the distance at which they were released. Percentage recapture was not significantly affected by ambient temperature or the sex of the moths. Only for the Geometroidea was the percentage recaptured slightly greater for the larger species. We found no significant differences between moth super-families with regard to the distance dependence of their attraction to light. Our data confirm that the radius of attraction of low powered light traps for moths is very small often even below 10 m. Thus, moths are good indicators of habitat quality and fragmentation as they are rarely attracted from distant habitats to such light traps.