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

Julia NIERMANN,Gunnar BREHM

doi:10.14411/eje.2022.004

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, 50Â°56Â´12ËN, 11Â°37Â´37ËE). 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 flux (LepiLED maxi: 1.34 W mixed radiation) attracted 37% more moths and 5% more species than a lamp with a lower radiant flux (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 significantly 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 efficient and results in larger catches than the use of a single strong lamp.

Highlights

With the increasing attention on the global decline in biodiversity, moths have received more attention as indicator organisms (e.g. Wirooks, 2004; Rákosy & Schmitt, 2011; Dar & Jamal, 2021)
All are equipped with eight Nichia power LEDs, the emission maxima of which are in the areas of maximum sensitivity of the photoreceptors of various Lepidoptera and other insects (Briscoe & Chittka, 2001)
The results confirm the expectation that a lamp with low radiant flux attracts fewer individuals and species than one with a high radiant flux

Summary

INTRODUCTION

With the increasing attention on the global decline in biodiversity, moths have received more attention as indicator organisms (e.g. Wirooks, 2004; Rákosy & Schmitt, 2011; Dar & Jamal, 2021). Used lamps for light-trapping include mercury vapour lamps or fluorescent tubes, but LED lamps designed for this purpose have become increasingly popular in the last few years They are attractive to insects, small, lightweight and use little energy (Brehm, 2017; Infusino et al, 2017), allowing the use of lightweight lithium batteries in the field. No studies have compared lamps which differed in the quantity of their radiant flux, but are otherwise identical Such lamps are already on the market for different applications: Many researchers want to use the most powerful lamp available to catch as many moths as possible in a short time, as reported by Brehm (2017). We expect the ranking maxi > UV > mini. (3) A UV lamp attracts a similar spectrum of moths as a lamp with different wavelengths because moths behave overall (see Brehm et al, 2021). (4) We expected similar numbers of individuals and species richness in the two grassland habitats investigated, but more moths at exposed sites because of the wider effective radius of the lamps than in sheltered sites in the vicinity of bushes

MATERIAL AND METHODS

Findings

DISCUSSION