Open Access

Ludger Wirooks

• Die gebräuchlichste und effektivste Methode zur Erfassung von Nachtfaltern ist der Lichtfang (MEIER 1992). Dieser Methode mangelt es allerdings an dem speziell in der Naturschutzpraxis wichtigen, unmittelbaren Flächenbezug. Dies liegt zum einen daran, dass es sich dabei um eine Anlockmethode handelt, zum anderen aber auch daran, dass bei Nachtfaltern noch weitgehend unbekannt ist, ob und inwieweit sich die Fluggebiete der Imagines mit den entsprechenden Präimaginalhabitaten decken. Aus diesen Gründen schlug MALICKY (1965: 371) vor, als Bezugsgröße von Lichtfangartenspektren gar nicht einzelne Biotope zu betrachten, sondern die „Gesamtheit der in der betreffenden Landschaft vorhandenen Biotope“, in denen dann alle Arten sicher bodenständig wären. Da bei naturschutzfachlichen Bewertungen aber normalerweise Biotope oder Biotopkomplexe und nicht Großlandschaften zu bewerten sind, wäre ein solcher biozönologischer Flächenbezug im praktischen Naturschutz kaum von Nutzen. In der vorliegenden Untersuchung wurde die mittels Lichtfang ermittelte räumliche Verteilung von Nachtfalterimagines mit der Verteilung ihrer Präimaginalstadien verglichen, um auf diesem Wege zu einer quantitativen Abschätzung des ökologischen Flächenbezugs von Lichtfangdaten zu gelangen.
• The object of this study was to evaluate the suitability of light-trapping methods for mapping and monitoring moths in the context of nature conservation and managing. The chief aim was to evaluate the size of a reference area the light-trap catches of moths can refer to as an area in which the light-trapped species can be regarded as indigenous in a synecological sense. To answer this question the small-scale spatial distributions of pre-imaginal and imaginal stages of moths were compared on the basis of field data obtained in a 16.8 ha study area situated to the west of the city of Aachen, Germany. Whilst pre-imaginal stages were searched by means of many different methods for a period of six years (1993–1998) throughout the whole study area, adult moths were light-trapped at a few selected sites during the years 1994 to 1995. They were sampled with the help of six weekly and simultaneously operated Minnesota-type light-traps equipped with 8-W blacklight lamps. In addition a so-called “gauze tower” with high-powered light sources was used fortnightly at one site in the centre of the study area. The results show that the species overlapping between the adult fauna of the light-trap sites and the pre-imaginal fauna of the related surrounding areas at first increased with expanding radius of the reference area, but eventually often met a maximum at a radius of about 50 to 200 m. This was due to the fact that the proportion of light-trapped species which can obviously reproduce within the related area increased with expanding radius while the proportion of the pre-imaginal fauna actually recorded in the associated light-traps decreased with increasing size of the reference area. Although the bigger proportion of light-trapped species can be assumed to be indidenous within the closer surroundings of a light trap there is a high probability of catching single non-indigenous species too. Therefore it is always necessary to differentiate the light-trapped species individually by their synecological status whatever the size of the chosen reference area may be. However, light-trapping cannot substitute the labour-intensive search for the larval stages in the context of ecological basic research, but it can nevertheless be a useful tool in applied ecological field studies.