The number of moths caught by light traps is affected more by microhabitat than the type of UV lamp used in a grassland habitat

Abstract

We compared the performance of three entomological LED lamps that differed in intensity and wavelength composition by using them to catch 2257 individuals of 161 species and 11 families of nocturnal Lepidoptera in two grassland habitats (dry grassland and orchard meadow). The study was carried out in June and July 2020 in the Jenzig conservation area (Jena, Germany, 50°56 ́12 ̋N, 11°37 ́37 ̋E). In each habitat, we sampled three microhabitats that were either exposed, moderately sheltered or sheltered. Data were analysed using generalized linear mixed models. A lamp with high radiant fl ux (LepiLED maxi: 1.34 W mixed radiation) attracted 37% more moths and 5% more species than a lamp with a lower radiant fl ux (LepiLED mini: 0.55 W mixed radiation). The maxi lamp also attracted 17% more moths and 6% more species than the same lamp with UV radiation only (LepiLED maxi switch UV mode: 0.59 W). However, the maxi lamp only performed signifi cantly better in exposed microhabitats, whereas the UV lamp performed similarly in the sheltered and moderately sheltered sites. The number of individuals caught in the dry grassland habitat was greater than in the orchard meadow (1288 vs. 969), whereas the number of species was similar in both habitats (120 vs. 128). Higher numbers of individuals were caught in the moderately sheltered sites than in the sheltered and exposed sites (935 vs. 773 vs. 549). The same trend was seen in the number of species (119 vs. 113 vs. 110). The communities of moths caught by traps with different lamps were similar. We conclude that light-trapping is a robust method that delivers comparable results even when different lamps are used. The use of several weak lamps is more effi cient and results in larger catches than the use of a single strong lamp.