Comparison between window traps and pan traps in monitoring flower-visiting insects in agricultural fields

Abstract

Sampling flower-visiting insects in agricultural fields at large spatial and temporal scales is significant for understanding local insect pollinator communities. The most commonly used method, pan trap, has been criticized due to its attractant bias. A window trap (also referred to as the flight-intercept trap) is a non-attractant sampling method, which has been applied in forests and grasslands, but rarely in agricultural fields. We aim to test whether we can replace pan traps with window traps in agricultural fields by comparing species richness and species composition between the two methods, and to show whether flower-visiting insects collected in both traps can reflect flower-visiting activity recorded by camera observation. We conducted a 2-year study to compare the performance of these sampling methods in an oilseed rape field. Results showed that the relative abundance of dominant flower-visiting species was highly correlated between the window trap and the pan trap samples, while window traps caught more individuals and higher (rarefied) species richness than pan traps. The species composition of window traps was more similar to each other than that of pan traps. The proportion of honey bees (Apis spp.) collected in both traps underestimated their flower-visiting activity recorded by camera observations, while sweat bees (Halictidae) and butterflies (Lepidoptera) were overestimated. Our study suggests that the window trap has the potential to serve as an alternative sampling method of flower-visiting insects to the pan trap. However, we need to be cautious when using specimens caught in both traps as a proxy of their flower-visiting activity.

Optimizing low-cost sampling of pollinator insects in oilseed rape fields

“…Our results suggested that both FITs and PTs are surprisingly similar in their per-cost effectiveness and coverage in trapping pollinators. Results showed that a single FIT caught more individuals and species than single PTs, agreeing with the prior study (Rubene et al, 2015;Shi et al, 2022b). It seems likely that the highly attractive oilseed rape reduces the catches of PTs, so nonattractant FITs are less impacted by this and collect more specimens per unit (Baum and Wallen, 2011;Vrdoljak and Samways, 2012;Prendergast et al, 2020).…”

“…Despite much prior research on the topic, there remain many gaps in our knowledge of effective monitoring for pollinating insects, especially in subtropical environments of Asia and for the multitude of passive trap methods (Cane et al, 2000;Campbell and Hanula, 2007;González et al, 2020;Van Drunen et al, 2022). The sampling performance of FITs and PTs, as two common passive pollinator sampling methods, has been assessed at limited scales (one oilseed rape field) previously and found flight interception trap outperform pan trap (more individuals and species collected per trap; Shi et al, 2022b). Here, we expanded on prior efforts by expanding sampling coverage and incorporating trait and semi-natural area analyses to determine whether these factors introduce biases.…”

“…Semi-natural habitat is defined as the habitat in the agricultural landscape where noncrop plants grow (Holland et al, 2016). Semi-natural habitats in this study include forest, shrub and grassland that embedded in the agricultural landscape and water bodies, like rivers and streams were not included in the analysis, as in prior studies in China (Zou et al, 2017;Shi et al, 2021Shi et al, , 2022b and abroad (Papanikolaou et al, 2017;Zou et al, 2017;Shi et al, 2021). The land-use data (forest, shrub, grassland and other) in the 1000 m radius for the focal oilseed rape field was collected using ground verification methods (Liu et al, 2016;Zou et al, 2017) in the spring of 2022.…”

eDNA metabarcoding of avocado flowers: ‘Hass’ it got potential to survey arthropods in food production systems?

“…pan, Malaise and vane traps), visual observation and active survey techniques (e.g. sweep netting; Gervais et al, 2018; Kearns & Inouye, 1993; Prado et al, 2017; Shi et al, 2022). Indeed, pan, Malaise and vane traps are some of the most commonly used methods to measure bee diversity in agroecosystems, largely because they provide a low‐cost means to sample multiple sites simultaneously (McCravy, 2018; Prado et al, 2017; Spafford & Lortie, 2013).…”

“…Studies using these passive survey methods have, for example, demonstrated the benefit of adjacent natural habitats for pollinator abundance and crop yield (see Klein et al, 2012; Morandin & Winston, 2006), and identified the inverse relationship between cultivated land use and wild pollinator diversity, particularly for wild bee species (see Bergholz et al, 2022; Zou et al, 2017). Unfortunately, passive sampling techniques often require extensive time commitments and increasingly rare specialist taxonomic expertise to morphologically identify the arthropod taxa collected or observed (Brown, 2020; Pardo & Borges, 2020; Shi et al, 2022). Furthermore, even when morphological identifications are possible, passive sampling techniques often have intrinsic biases in the taxa that are captured.…”