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Increasing evidence for insect biodiversity decline requires an identification of the causes but also an improved understanding of the limitations of the various underlying sampling methods. Trap comparisons foster comparability of larger-scale biodiversity studies by providing a deeper understanding of the variations in species abundances and trait compositions due to variations in trap characteristics. In our study, we compared five Malaise trap types on their catchability of butterfly species and noctuid moths and examined for the butterflies how this can be related to traits. We showed marked differences in species and trait occurrence in the samples of the different trap types which seemed to be influenced by roof colour (white, black) and trap shape (Townes trap: high, wide roof, Bartak trap: low, narrow roof). We found most butterfly species and most butterfly biomass in the white-roofed Townes trap. All butterfly traits were represented with most individuals in this trap. Compared with its black counterpart, it showed increased catches for pale butterflies and forest species. We found that dark-roofed traps captured fewer butterfly species and had a lower butterfly biomass. Townes traps captured more butterflies with larger wingspans, egg-laying locations higher above ground, and tree feeding behaviour compared to Bartak traps. Depending on the season and habitat, the differences in species capture may affect overall insect biomass.
1. Recent reports on insect decline have highlighted the need for long-term data on insect communities towards identifying their trends and drivers.
2. With the launch of many new insect monitoring schemes to investigate insect communities over large spatial and temporal scales, Malaise traps have become one of the most important tools due to the broad spectrum of species collected and reduced capture bias through passive sampling of insects day and night. However, Malaise traps can vary in size, shape, and colour, and it is unknown how these differences affect biomass, species richness, and composition of trap catch, making it difficult to compare results between studies.
3. We compared five Malaise trap types (three variations of the Townes and two variations of the Bartak Malaise trap) to determine their effects on biomass and species richness as identified by metabarcoding.
4. Insect biomass varied by 20%–55%, not strictly following trap size but varying with trap type. Total species richness was 20%–38% higher in the three Townes trap models compared to the Bartak traps. Bartak traps captured lower richness of highly mobile taxa but increased richness of ground-dwelling taxa. The white roofed Townes trap captured a higher richness of pollinators.
5. We find that biomass, total richness, and taxa group specific richness are all sensitive to Malaise trap type. Trap type should be carefully considered and aligned to match monitoring and research questions. Additionally, our estimates of trap type effects can be used to adjust results to facilitate comparisons across studies.
1. In times of insect decline, sampling programmes are fundamental for monitoring and protecting insect populations. Different types of traps are currently used for insect monitoring, which makes trap selection more challenging and impedes the comparability of results among methods.
2. Trap comparisons, which reveal the species richness, complementarity and costs for the materials and operation of different trap types, help identify sampling designs that ensure (cost-)efficient insect capture.
3. For our study, we selected five sampling techniques for flying insects: canopy Malaise traps (CAMTs), caterpillar traps, branch sampling and white and blue pan traps. We compared them across four habitats (forest, margin and centre of short rotation coppices and maize fields) using detected Barcode Index Numbers (BINs). Comparisons were performed for the total arthropod community and separately for the Coleoptera, Diptera, Lepidoptera and Hymenoptera orders.
4. Our trap selection demonstrated high complementarities of 66–77% depending on the habitat. Our findings indicate that, in most cases, CAMTs, branch sampling and caterpillar traps were the most effective and cost-efficient options when used individually or in combination. Caterpillar traps were particularly effective in forests and detected far more taxa than only lepidopterans. Pan traps demonstrated the lowest species richness and poorest cost efficiency. Nevertheless, it is important to consider individual groups and habitats, such as Diptera, Coleoptera and maize fields, for which pan traps can also be an effective method.
