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To understand change in global biodiversity patterns requires large‐scale, long‐term monitoring. The ability to draw meaningful comparison across studies is severely hampered by extensive variation in the design of the sampling equipment and how it is used. Here, we present a meta‐analysis and description highlighting this variation in a common, widely used entomological survey technique. We report a decline in the completeness of methodological reporting over a 20‐year period, while there has been no clear reduction in the methodological variation between researchers using pitfall traps for arthropod sampling. There is a growing need for improved comparability between studies to facilitate the generation of large‐scale, long‐term biodiversity datasets. However, our results show that, counterproductive to this goal, over the last 20 years there has little progress in reducing the methodological variation. We propose a standardized pitfall trap design for the study of ground‐active arthropods. In addition, we provide a table to promote a more standardized reporting of the key methodological variables. Widespread adoption of more standardized methods and reporting would facilitate more nuanced analysis of biodiversity change. The use of pitfall trapping for monitoring ground‐active arthropods is a common technique in ecological research, but suffers from extensive variation between researchers and reporting of the methodology is often incomplete. This review highlights this variation in both trap design and reporting completeness and proposes a standardized pitfall trap design. It is hoped that uptake of this design would facilitate future comparison between studies and allow investigation of biodiversity at larger spatial and temporal scales than would be easily achievable from individual researchers.

Sampling is one of the most important and fundamental processes in field biology. Among many sampling methods in entomology, window traps have long been considered one of the most effective and standardized methods. Unfortunately, the DNA quality of samples collected by window traps is typically low due to incursion by water, mainly via rainfall. Water cannot be avoided in long‐term surveys, even with a roof, due to wind and condensation. As we move into the genomics era, this shortfall in DNA quality has become problematic for molecular biomonitoring, and solutions are urgently needed. In this study, we developed the Water‐Exclusion Trap (WET), a 3D printable long‐term storable bottom collector for window or pitfall traps. The collection medium in WETs does not dilute because water is excluded and evaporation is limited, maximizing DNA preservation. Our field tests show that the WET outperforms conventional traps in preserving DNA quality. Insect samples preserved in WETs in the field had significantly higher PCR success rates and DNA Integrity Numbers compared to conventional traps. The WET addresses a critical challenge in the use of window traps, DNA degradation caused by water intrusion, and represents a significant advancement in fieldwork for genomic research in entomology. We provide the 3D printing template of the WET, enabling immediate, free use for all. Furthermore, it can be easily customized for different environments and purposes, and can be adapted to a variety of other traps, including pitfall traps, funnel traps and more.

Context Organic farming is increasingly used worldwide in recent decades, but the role of this farming system in shaping the trophic structure of arthropod communities remains poorly understood, especially at different spatial scales. Therefore, the contribution of landscape heterogeneity in shaping arthropod’s trophic guilds remain understudied. Objectives In this study, we assessed how the evenness, the abundance and the taxonomic richness of arthropod trophic groups were shaped by the local farming system, landscape heterogeneity (including the percentage of semi-natural habitats and organic fields), and their interaction. Methods Arthropod’s trophic guilds (ground and vegetation-dwelling) were sampled in 20 spatial independent pairs of conventional (CF) and organic (OF) fields located in Brittany (Western France) by using pitfall traps and sweep nets replicated in time and space. Results A total of 95,822 arthropods belonging to 197 taxonomic groups were sampled. Farming system has a strong overall positive effect on the community structure of both ground- and vegetation-dwelling arthropods. Landscape heterogeneity, alone and in interaction with farming systems, affected positively the diversity and abundance of most trophic groups for both ground- and vegetation-dwelling arthropods. Organic farming therefore affected the trophic composition of arthropod communities not only locally, but also at the landscape scale. Conclusions Our study highlights the strong positive effect of farming system and the landscape heterogeneity on arthropod communities and more importantly the interconnection between different spatial scales in this process. Taking these aspects into account is therefore crucial in understanding arthropod community dynamics in agroecosystems.

Pitfall traps are widely used for sampling ground-dwelling arthropods. Their sampling efficiency is affected by several factors, e.g. material, size and modification of parts of the trap and sampling design. Pitfall trap sampling is also affected by the accumulation of plant litter in the traps, rain fall and by-catches of small vertebrates, which may cause a bias in the catch by obstructing traps or attracting certain insects. A roof that prevents rain and plant litter entering a trap, prevents dilution of the preservative and escape of arthropods. The main goal of present study was to compare the effect of four types of differently combined funnel and roof pitfall traps on the capture efficiency of epigeal arthropods. We found that a funnel and/or a roof had no effect on spider catches. Total abundance of large carabids and thus the total abundance of ground beetles was lower in funnel pitfall traps without a roof than in other types of traps. However, funnel pitfall traps with roofs collected significantly more carabid beetles, especially individuals of those species that are large or good fliers. We conclude that funnel pitfall traps with roofs have no negative effects on capture efficiency of ground beetles and spiders, therefore application of this sampling technique is strongly recommended.

Roller dung beetles play a pivotal role in the nutrient distribution in soil and secondary dispersal of seeds. Dung beetles are sampled either using a dung-baited pitfall trap or an exposed dung pile on the ground. While the former method is useful for a rapid survey of dung beetles, information on the ecology and behaviour of dung beetles can be lost, which the latter method provides, but underestimates species diversity due to its inefficiency in trapping rollers. Efficiency of a new method for sampling rollers—installing guarding pitfall traps around dung piles—is assessed in three habitats—contiguous tropical rainforests, fragmented forests, and disturbed used home gardens—and two diel periods—day and night. Five guarding pitfall traps were installed at 50 cm radius around dung piles. About 98% of the total rollers were sampled in pitfall traps. The habitats were similar when the roller catches of only dung piles—conventional approach—were analyzed, but were different when the rollers of guarding pitfall traps were considered. The roller abundance was negatively affected by forest fragmentation and land-use change. About 98% of the rollers were collected at daytime. Using guarding pitfall traps around dung piles is highly recommended for dung beetle diversity studies.

We provide an inventory of the spiders (Arachnida: Araneae) inhabiting the Val Grande National Park (NW - Italy) based on literature data, reliable iNaturalist observations and an original survey conducted between 2018 and 2019 in the frame of the “Biodiversity Monitoring Project” (BMP). In total, we report 157 species belonging to 92 genera and 25 families, including 11 new records for Piemonte and 103 new records for the Province of Verbano-Cusio-Ossola. Linyphiidae and Gnaphosidae were the most represented families, consistently with other protected areas across the Alps. Most species exhibited a Palearctic or European distribution, with a small proportion of endemics. Based on the original data gathered with standardized transects of pitfall traps we analysed species richness and abundance along the altitudinal gradient, revealing a general increasing trend with elevation. We also analyse the relationship between species composition and environmental variables using Canonical Correspondence Analysis (CCA) and revealed that species composition was significantly influenced by elevation and habitat type, highlighting clear ecological structuring along the altitudinal gradient. Beyond the faunistic contribution, we highlight the importance of faunal inventories for biodiversity conservation, particularly for lesser-known taxa like spiders, whose protection depends on accurate occurrence data within protected areas.

DNA metabarcoding is increasingly used to analyze the diet of arthropods, including spiders. However, high sensitivity to DNA contamination makes it difficult to apply to organisms obtained from mass‐sampling methods such as pitfall traps. An alternative is to hand‐sample spiders, but it is unclear how effectively this prevents external contamination, especially with new knowledge showing the wide spread of eDNA in the environment. Protocols using bleach to remove external DNA have been tested on several invertebrates, though testing with both mass‐sampling methods and spiders is lacking. Here, we used wolf spiders (Lycosidae) to assess the risk of external DNA contamination from pitfall trapping and hand sampling, and the efficacy of bleach decontamination. We first conducted a contamination experiment where we placed spiders in pitfall traps containing trapping medium and a nonprey insect species to simulate external DNA contamination. We also compared sampling methods by collecting spiders using pitfall traps and hand sampling. Spiders from the contamination experiment and sampling method comparison were either bleached or untreated, then metabarcoded using multiple primer pairs. The contamination experiment resulted in the contamination of almost all spiders from pitfall traps, which was successfully eliminated with bleaching. Interestingly, there was no difference in the number of amplicon sequence variants (ASVs) detected per spider between pitfall trapping and hand sampling but bleaching resulted in significantly fewer ASV detections for both methods. Additionally, bleaching, but not sampling method, affected the taxonomic diet composition for both hand‐sampled and pitfall‐trapped spiders, indicating similar levels of external contamination. Our results are the first to confirm that DNA metabarcoding can be used together with bleaching for spiders sampled from pitfall traps, and that hand sampling does not necessarily exclude external DNA contamination. Thus, diet studies using metabarcoding should address the risk of external contamination with field‐sampled arthropods, regardless of sampling method. We used wolf spiders (Lycosidae) to test the risk of external DNA contamination from pitfall trapping and hand sampling, the effectiveness of bleach for eliminating external DNA contamination, and possible adverse effects of bleaching on prey DNA recovery. We found that bleaching was effective in removing external DNA contamination without affecting prey DNA. We also found that hand‐sampled spiders had similar levels of contamination as those obtained from pitfall traps, indicating that external DNA contamination is a concern for arthropods destined for DNA metabarcoding, regardless of sampling method.

The snouted harvester termite ( Trinervitermes trinervoides (Sjöstedt, 1911)) is a widespread grass-eating termite species that constructs thermoregulated dome-shaped mounds. However, little is known about the influence of these mounds on the arthropod assemblage structure in the surrounding grassland matrix, and whether the mounds represent ecological islands. Spiders and springtails are two ecologically important arthropod groups often associated with termites or their mounds. We investigated their assemblage composition inside and around active and abandoned T. trinervoides mounds in a central South African grassland. In total, 838 spiders (59 spp., 22 families) and 217 857 springtails (24 spp., 9 families) were collected from 96 pitfall traps, placed at four microhabitats in and around each of 12 active and 12 abandoned mounds during March 2019. The most abundant and species-rich spider families include the Gnaphosidae (n = 270, 10 spp.), Zodariidae (n = 86, 7 spp.), Lycosidae (n = 86, 6 spp.) and Salticidae (n = 77, 5 spp.), whereas the springtail fauna was dominated by Brachystomellidae (n = 56 521, 1 species), Bourletiellidae (n = 49 573, 7 species), Sminthurididae (n = 44 491, 3 species), Isotomidae (n = 32 288, 1 species) and Entomobryidae (n = 26 216, 7 species). Indicator analysis showed that the spiders Zelotes sclateri Tucker, 1923, Heliocapensis termitophagus (Wesołowska & Haddad, 2002) and Scytodes elizabethae Purcell, 1904 are associated with abandoned mounds, but no springtails showed an association based on the IndVal analysis of the eight microhabitats (lumped data), even though the undescribed Cyphoderus sp. were mostly collected inside active mounds. The mounds thus had a negligible influence on the spatial distribution of springtails in the surrounding grassland. The different spider and springtail assemblages sampled indicate that both active and abandoned mounds function as ecological islands in grasslands, but that mound size does not affect their abundance or species richness in the different microhabitats sampled.

The climbing abilities of two bed bug species, Cimex lectularius L. and Cimex hemipterus (F.), were determined by evaluating their escape rates from smooth surface pitfall traps using four commercial bed bug monitors (Verifi Bed Bug Detector, ClimbUp Insect Interceptor, BlackOut Bed Bug Detector, and SenSci Volcano Bed Bug Detector). All detectors were used in the absence of lures or attractants. Unlike C. lectularius, adult C. hemipterus were able to escape from all traps. On the other hand, no or a low number nymphs of both species escaped, depending on the evaluated traps. Examination of the vertical friction force of adults of both species revealed a higher vertical friction force in C. hemipterus than in C. lectularius. Scanning electron microscope micrograph observation on the tibial pad of adult bed bugs of C. hemipterus showed the presence of a greater number of tenent hairs on the tibial pad than on that of adult C. lectularius. No tibial pad was found on the fourth and fifth instars of both species. Near the base of the hollow tenent hairs is a glandular epithelium that is better developed in adult C. hemipterus than in adult C. lectularius. This study highlights significant morphological differences between C. lectularius and C. hemipterus, which may have implications in the monitoring and management of bed bug infestations.

ContextDeclining biodiversity in agricultural landscapes has increased the need for research and monitoring of insect abundance and diversity at the landscape level.ObjectivesWe investigated the accuracy of different spatial sampling designs in estimating landscape-level abundance and species richness of carabids in agricultural landscapes and, further, which sample size per landscape section was required and whether dominating land use or landscape subdivision affected accuracy and required sample size.MethodsWe developed a simulation model that created raster maps of agricultural landscapes, compiled local carabid communities (species composition and abundances) within raster cells and simulated the sampling of carabids with pitfall traps using different spatial sampling designs and sample sizes between 4 and 49 sampling points per landscape section. Spatial sampling designs included random, systematic grid-based, stratified and clustered schemes.ResultsTo estimate landscape-level abundance, area-proportional stratified random sampling was most accurate followed by systematic grid-based designs. A sample size of 25 appeared to be the best trade-off between accuracy and sampling cost. Accuracy was not affected substantially by landscape characteristics in most cases. With respect to species richness, all designs except for clustered sampling had comparable accuracies, but even 49 samples were not sufficient to detect 80% of the species.ConclusionSystematic grid-based designs are generally recommendable for sampling of carabids in agricultural landscapes and, in case a carabid-specific habitat classification is available, area-proportional stratified random sampling provides optimal accuracy for estimating landscape-level abundance. For assessment of species richness, large sample size is more important than spatial sampling design.