Methods for interpreting  emergence trap specimen data for the study of ground nesting bees (Hymenoptera:  Anthophila)

Abstract

Emergence traps have increasingly been used to study ground nesting bees. They offer an advantage over other methods, such as netting or passive traps, because they can directly measure ground nesting bees at a landscape scale. However, emergence trapping for ground nesting bees has limitations, including low catch rates and data that is difficult to interpret. For example, emergence traps catch a combination of actively nesting bees, newly emerging bees from nests provisioned the previous year, overwintering bees, and incidental bees, such as non-ground-nesting species or bees that were simply sleeping on vegetation. Further, a single emergence trap can capture many specimens from a single nest due to the presence of workers, newly emerging reproductives (gynes), or multiple siblings from a nest provisioned the previous year. Due to these factors, a thorough knowledge of the life history of bee species collected is necessary to accurately filter and interpret the data. Here, we provide methods to determine whether bee specimens caught from emergence traps came from nests. Using a combination of trap data, life-history characters, and estimates of bee age, we classify bees as newly emerging, active nests, or incidentally caught. This will allow researchers to reduce the risk of spurious inferences that may over- or under-estimate bee nesting. Many areas of future research remain, particularly studies on the efficacy of emergence traps for ground-nesting bee research as well as a glaring need to better document the life-history of many bee species. Abstract content goes here

Prescribed fire increases the number of ground‐nesting bee nests in tallgrass prairie remnants

“…This contrasts to other emergence trap studies that analyse total bee abundance or that rely on trap‐level presence‐absence data (Cope et al, 2019; Kim et al, 2006; Manion, 2020; May, 2015, Rivers et al, 2018; Sardiñas & Kremen, 2014; Sardiñas et al, 2016; Ulyshen et al, 2021). Our methodology is useful for describing patterns of within‐year nest site choices by ground‐nesting bees that can be applied to other studies using emergence traps (Portman, Brokaw, & Cariveau, 2022). This likely provided more robust results by excluding incidental captures and prevented inflating nesting counts due to the collection of many individuals of social species in traps.…”

“…A major advancement of this research is that we estimated the number of nests in burned and unburned patches that were actively being used by ground‐nesting bees the year of the study (hereafter ‘active nests’), instead of inferring based on bee abundance or the presence or absence of bees within a trap. This analysis allowed us to avoid over‐ or under‐ estimating nest densities within our treatments (Portman, Brokaw, & Cariveau, 2022).…”

“…Because the burn treatment was in the spring of 2019, we also excluded bees that were likely emerging from nests provisioned the previous year, which were characterised by the presence of single or multiple unworn solitary ground‐nesting individuals of the same species that overwinter in the natal cell, all caught in the same trap. Cleptoparasites, stem‐nesting bees, cavity‐nesting species and males were excluded from the analysis because they do not excavate their own nests underground (see Portman, Brokaw, & Cariveau, 2022) for a full description of this methodology).…”

Observations on nesting preferences and success in two species of Anthophora (Hymenoptera: Apidae)

“…Additional species may nest in both horizontal and vertical faces, including Panurgus calcaratus (Scopoli, 1763) ( Rozen 1967) and Lasioglossum morio (Fabricius, 1793) ( Westrich 2022), but our knowledge is limited by few natural history accounts for all but the best-known species ( Harmon-Threatt 2020); since most studies used one site, environment-dependent variation may be entirely unaccounted for in most species, and our knowledge is further limited primarily to higher-income countries ( Orr et al 2020). With further study of the natural history of these and other urban-adapted species ( Orr et al 2022; Portman et al 2022), it may also be possible to better understand their nest site preferences and design cities better equipped for bees.…”

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The persistence of a bee species in any environment is contingent upon the resources it requires. Among such resources, nesting substrates are of central but understudied importance (LinsLey 1958;Harmon-THreaTT 2020;orr et al 2022;PorTman et al 2022). For example, cavity-nesting bees require logs with beetle holes, pithy-stemmed woody plants, etc., while ground nesters may require specific substrates and other local parameters that meet their requirements (LinsLey 1958;micHener et al 1958).

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