Bumble Bee Bombus Impatiens Research Articles

ECR Spotlight – Kelton Verble and Ellen Keaveny

ECR Spotlight is a series of interviews with early-career authors from a selection of papers published in Journal of Experimental Biology and aims to promote not only the diversity of early-career researchers (ECRs) working in experimental biology but also the huge variety of animals and physiological systems that are essential for the ‘comparative’ approach. Kelton Verble and Ellen Keaveny are authors on ‘A rapid return to normal: temporal gene expression patterns following cold exposure in the bumble bee Bombus impatiens’, published in JEB. Kelton is a PhD candidate in the lab of Dr Jeffrey Lozier at The University of Alabama, USA, investigating the transcriptomics and epigenomics underlying thermal tolerance in bumble bees. Ellen is a PhD candidate in the lab of Michael Dillon at the University of Wyoming, USA, investigating how temperature affects bumble bees at cellular, organismal, population and community levels.

Insect Flight Energetics and the Evolution of Size, Form, and Function.

Flying insects vary greatly in body size and wing proportions, significantly impacting their flight energetics. Generally, the larger the insect, the slower its flight wingbeat frequency. However, variation in frequency is also explained by differences in wing proportions, where larger-winged insects tend to have lower frequencies. These associations affect the energy required for flight. The correlated evolution of flight form and function can be further defined using a lineage of closely related bee species varying in body mass. The decline in flight wingbeat frequency with increasing size is paralleled by the flight mass-specific metabolic rate. The specific scaling exponents observed can be predicted from the wing area allometry, where a greater increase (hyperallometry) leads to a more pronounced effect on flight energetics, and hypoallometry can lead to no change in frequency and metabolic rate across species. The metabolic properties of the flight muscles also vary with body mass and wing proportions, as observed from the activity of glycolytic enzymes and the phospholipid compositions of muscle tissue, connecting morphological differences with muscle metabolic properties. The evolutionary scaling observed across species is recapitulated within species. The static allometry observed within the bumblebee Bombus impatiens, where the wing area is proportional and isometric, affects wingbeat frequency and metabolic rate, which is predicted to decrease with an increase in size. Intraspecific variation in flight muscle tissue properties is also related to flight metabolic rate. The role of developmental processes and phenotypic plasticity in explaining intraspecific differences is central to our understanding of flight energetics. These studies provide a framework where static allometry observed within species gives rise to evolutionary allometry, connecting the evolution of size, form, and function associated with insect flight.

Debunking wasp pollination: Wasps are comparable to bees in terms of plant interactions, body pollen and single‐visit pollen deposition

Abstract Wasps are understudied in their contribution to pollination services. In order to better understand the ecological contribution of wasp communities to plant pollination, we conducted three studies to compare bees and wasps by (1) the plant communities visited in agricultural and prairie environments, (2) body pollen composition as an indirect measure of pollination and (3) a single‐visit deposition study as a direct measure of pollination in the plant species complex Solidago canadensis. We found wasps visit a distinct early‐blooming exotic plant community from bees but have overlapping use of late‐blooming native plants and similar network interaction metrics. This suggests wasps may fill an ecological niche distinct from bees, while also serving as common native plant visitors. We also found that body pollen density and pollen fidelity in four and five (out of six) wasp families, respectively, were comparable to or greater than the bee family Colletidae. Three wasp families also showed comparable to or greater visit fidelity than two (out of five) bee families examined. These results suggest wasps may carry and potentially deliver substantial pollen to specific plants. In addition, controlled single‐visit deposition revealed the paper wasp Polistes fuscatus deposits a similar amount of pollen grains as the bumble bee Bombus impatiens, suggesting surprisingly high pollination efficiency that warrants further investigation. Our multi‐pronged study shows the importance of investigating the role of wasps as pollinators, especially by focusing on direct plant‐pollination metrics to determine wasp pollination efficacy.

Gut Transplants from Bees Fed an Antipathogenic Pollen Diet Do Not Confer Pathogen Resistance to Recipients.

Pollinators are threatened by diverse stressors, including microbial pathogens such as Crithidia bombi. Consuming sunflower pollen dramatically reduces C. bombi infection in the bumble bee Bombus impatiens, but the mechanism behind this medicinal effect is unclear. We asked whether diet mediates resistance to C. bombi through changes in the gut microbiome. We hypothesized that sunflower pollen changes the gut microbiome, which in turn reduces Crithidia infection. To test this, we performed a gut transplant experiment. We fed donor bees either a sunflower pollen treatment or buckwheat pollen as a control treatment and then inoculated recipient bees with homogenized guts from either sunflower-fed or buckwheat-fed donor bees. All recipient bees were then fed a wildflower pollen diet. Two days after the transplant, we infected recipients with C. bombi, and 2days later, we provided another donor gut transplant. To quantify infection, we performed both fecal screens and dissections of the recipient bees. We found no significant differences in C. bombi infection intensity or presence between bees that received sunflower-fed microbiomes versus buckwheat-fed microbiomes. This suggests that sunflower pollen's effects on pathogen resistance are not mediated by gut microbiota.

Plant secondary metabolite has dose‐dependent effects on bumblebees

The presence of secondary metabolites in flower nectar can mediate interactions between plants, pollinators, herbivores, and microbes. Milkweeds range in concentrations of cardenolides in flower nectar from ~ 1 to 100 ng μl–1. Using three different behavioral assays with bumblebees Bombus impatiens, we examined the impacts of the commercially available cardenolide ouabain at the range of concentrations at which cardenolides naturally occur in milkweeds. We show that after four days of exposure bees in consumption assays drank more of a nectar solution with a low ouabain concentration of 10 ng μl–1 than the control sucrose nectar, and over the course of the experiment bees consumed less of the 100 ng μl–1 ouabain solution than the control. Bee activity levels in Petri dish arena assays were not impacted by ouabain consumption, even at the highest concentrations; however, in free‐flying choice assays, bees preferentially visited artificial flowers containing 10 ng μl–1 ouabain more than flowers with sucrose control, or flowers with 100 ng μl–1 of ouabain. We therefore conclude that cardenolides may provide plants advantages to pollination at the low end of the naturally occurring range of concentrations for cardenolides, but may be costly to plants at the high end of the range. This research highlights that secondary metabolites in nectar may be under selection to be maintained at low concentrations, and species with high concentrations of secondary metabolites may be under conflicting selection pressures to maintain high circulating levels to deter herbivores at the cost of reduced pollination.

Investigating the influence of diet diversity on infection outcomes in a bumble bee (Bombus impatiens) and microsporidian (Nosema bombi) host-pathogen system.

Diet can have an array of both direct and indirect effects on an organism's health and fitness, which can influence the outcomes of host-pathogen interactions. Land use changes, which could impact diet quantity and quality, have imposed foraging stress on important natural and agricultural pollinators. Diet related stress could exacerbate existing negative impacts of pathogen infection. Accounting for most of its nutritional intake in terms of protein and many micronutrients, pollen can influence bee health through changes in immunity, infection, and various aspects of individual and colony fitness. We investigate how adult pollen consumption, pollen type, and pollen diversity influence bumble bee Bombus impatiens survival and infection outcomes for a microsporidian pathogen Nosema (Vairimorpha) bombi. Experimental pathogen exposures of larvae occurred in microcolonies and newly emerged adult workers were given one of three predominantly monofloral, polyfloral, or no pollen diets. Workers were assessed for size, pollen consumption, infection 8-days following adult-eclosion, survival, and the presence of extracellular microsporidian spores at death. Pollen diet treatment, specifically absence of pollen, and infection independently reduced survival, but we saw no effects of pollen, pollen type, or pollen diet diversity on infection outcomes. The latter suggests infection outcomes were likely already set, prior to differential diets. Although infection outcomes were not altered by pollen diet in our study, it highlights both pathogen infection and pollen availability as important for bumble bee health, and these factors may interact at different stages of bumble bee development, at the colony level, or under different dietary regimes.

Consequences of microsporidian prior exposure for virus infection outcomes and bumble bee host health.

Host-parasite interactions do not occur in a vacuum, but in connected multi-parasite networks that can result in co-exposures and coinfections of individual hosts. These can affect host health and disease ecology, including disease outbreaks. However, many host-parasite studies examine pairwise interactions, meaning we still lack a general understanding of the influence of co-exposures and coinfections. Using the bumble bee Bombus impatiens, we study the effects of larval exposure to a microsporidian Nosema bombi, implicated in bumble bee declines, and adult exposure to Israeli Acute Paralysis Virus (IAPV), an emerging infectious disease from honey bee parasite spillover. We hypothesize that infection outcomes will be modified by co-exposure or coinfection. Nosema bombi is a potentially severe, larval-infecting parasite, and we predict that prior exposure will result in decreased host resistance to adult IAPV infection. We predict double parasite exposure will also reduce host tolerance of infection, as measured by host survival. Although our larval Nosema exposure mostly did not result in viable infections, it partially reduced resistance to adult IAPV infection. Nosema exposure also negatively affected survival, potentially due to a cost of immunity in resisting the exposure. There was a significant negative effect of IAPV exposure on survivorship, but prior Nosema exposure did not alter this survival outcome, suggesting increased tolerance given the higher IAPV infections in the bees previously exposed to Nosema. These results again demonstrate that infection outcomes can be non-independentwhen multiple parasites are present, even when exposure to one parasite does not result in a substantial infection.

Developing and Evaluating a New Method and Apparatus for Examining Bumble Bee Foraging Behavior

A key question in pollination biology is that of how pollinators identify and choose foraging patches. Several approaches have been employed for this, including field studies and large greenhouse flight chambers. Most methods used to date are limited, though, by reliance on a combination of artificial flowers, large spatial scales, or lack of spatially distinct floral patches. To address this issue, we designed and tested a y-maze flight arena and tested it using the bumblebee Bombus impatiens and canola plants. Our results indicate that the system is not biased by environmental conditions, or by an innate “handedness” of Bombus impatiens. We found that bees made all the expected patch choices when presented with soil, plants without flowers, or plants with flowers. This new method is important and useful as it allows researchers to ask questions of both plant health and insect behavior and the chamber system is modular allowing for simple changes to the setup to focus on different questions. • Y-maze flight arena was designed to evaluate foraging behavior on intact plants. • No evidence of side preference in individual bees. • Behaviors observed in the y-maze appear to correspond to behaviors observed in other settings.

Comparative analysis of 3 pollen sterilization methods for feeding bumble bees.

Pollen is an essential component of bee diets, and rearing bumble bees (Bombus spp.) for commercial use necessitates feeding pollen in mass quantities. This pollen is collected from honey bee (Apis mellifera L.) colonies because neither an artificial diet nor an economical, large-scale pollen collection process from flowers is available. The provenance of honey bee-collected pollen is often unknown, and in some cases has crossed international borders. Both deformed wing virus (DWV) and the fungal pathogen Ascosphaera apis (Claussen) Olive & Spiltoir (cause of chalkbrood disease); occur in honey bee-collected pollen, and infections have been observed in bumble bees. We used these pathogens as general surrogates for viruses and spore-forming fungal diseases to test the efficacy of 3 sterilization methods, and assessed whether treatment altered pollen quality for the bumble bee. Using honey bee-collected pollen spiked with known doses of DWV and A. apis, we compared gamma irradiation (GI), ozone fumigation (OZ), and ethylene oxide fumigation (EO) against an untreated positive control and a negative control. Following sterilization treatments, we tested A. apis spore viability, detected viral presence with PCR, and tested palatability to the bumble bee Bombus impatiens Cresson. We also measured bacterial growth from pollens treated with EO and GI. GI and EO outperformed OZ treatment in pathogen suppression. EO had the highest sterilizing properties under commercial conditions and retained palatability and supported bee development better than other treatments. These results suggest that EO sterilization reduces pathogen risks while retaining pollen quality as a food source for rearing bumble bees.

Commercial Bombus impatiens colonies function as ecological traps for wild queens

Abstract In response to anthropogenic environmental change, the cues that animals use throughout their lifecycle to optimize fitness may become unreliable, resulting in an ecological trap. Here we investigated whether commercial bumble bee Bombus impatiens colonies managed for early spring crop pollination act as ecological traps for wild nest‐searching Bombus queens by subverting their natural nest usurpation behaviour. An average of 10 dead wild queens were recovered from each standard colony during the 2‐week period of the experiment, but colonies with queen excluders were successful in preventing wild queen deaths. The use of queen excluders did not impact colony performance in terms of resident queen survival, colony reproduction, colony weight gain or worker body size. Sites where wild nest‐searching queens were small had higher rates of failed usurpation, suggesting smaller‐sized queens are disproportionately at risk from failed usurpation. Furthermore, sites where commercial colonies without queen excluders were introduced for spring crop pollination had fewer bumble bee visits to a later‐blooming crop compared to sites without commercial colonies. Synthesis and applications. Our findings reveal a novel mechanism by which commercial colonies can negatively impact wild bumble bee populations and their pollination services. At the same time, we demonstrate a simple and inexpensive risk mitigation tool—a queen excluder—was 100% effective at eliminating this risk without compromising colony performance. Commercial colonies used outdoors during the bumble bee nest‐searching period should be fit with queen excluders to prevent negative impacts on wild pollinator communities and their services.

The diversity, evolution, and development of setal morphologies in bumble bees (Hymenoptera: Apidae: Bombus spp.).

Bumble bees are characterized by their thick setal pile that imparts aposematic color patterns often used for species-level identification. Like all bees, the single-celled setae of bumble bees are branched, an innovation thought important for pollen collection. To date no studies have quantified the types of setal morphologies and their distribution on these bees, information that can facilitate understanding of their adaptive ecological function. This study defines several major setal morphotypes in the common eastern bumble bee Bombus impatiens Cresson, revealing these setal types differ by location across the body. The positions of these types of setae are similar across individuals, castes, and sexes within species. We analyzed the distribution of the two most common setal types (plumose and spinulate) across the body dorsum of half of the described bumble bee species. This revealed consistently high density of plumose (long-branched) setae across bumble bees on the head and mesosoma, but considerable variation in the amount of metasomal plumosity. Variation on the metasoma shows strong phylogenetic signal at subgeneric and smaller group levels, making it a useful trait for species delimitation research, and plumosity has increased from early Bombus ancestors. The distribution of these setal types suggests these setae may serve several functions, including pollen-collecting and thermoregulatory roles, and probable mechanosensory functions. This study further examines how and when setae of the pile develop, evidence for mechanosensory function, and the timing of pigmentation as a foundation for future genetic and developmental research in these bees.

The flavonoid rutin protects the bumble bee Bombus impatiens against cognitive impairment by imidacloprid and fipronil.

ABSTRACTThe ongoing decline of bee populations and its impact on food security demands integrating multiple strategies. Sublethal impairments associated with exposure to insecticides, affecting the individual and the colony levels, have led to insecticide moratoria and bans. However, legislation alone is not sufficient and remains a temporary solution to an evolving market of insecticides. Here, we asked whether bees can be prophylactically protected against sublethal cognitive effects of two major neurotoxic insecticides, imidacloprid and fipronil, with different mechanisms of action. We evaluated the protective effect of the prophylactic administration of the flavonoid rutin, a secondary plant metabolite, present in nectar and pollen, and known for its neuroprotective properties. Following controlled or ad libitum administration of rutin, foragers of the North American bumble bee Bombus impatiens received oral administration of the insecticides at sublethal realistic dosages. Learning acquisition, memory retention and decision speed were evaluated using olfactory absolute conditioning of the proboscis extension response. We show that the insecticides primarily impair acquisition but not retention or speed of the conditioned proboscis extension response. We further show that the administration of the flavonoid rutin successfully protects the bees against impairments produced by acute and chronic administration of insecticides. Our results suggest a new avenue for the protection of bees against sublethal cognitive effects of insecticides.

Examining the individual and additive effects of cold storage and CO2 narcosis on queen survival and reproduction in bumble bees

Diapause is a pre-programmed arrest of development allowing insects to survive in unfavorable environments. In adult insects, diapause termination is often followed by a reallocation of macronutrients and a transition to reproduction, and in some insects, this transition can be achieved using narcosis with CO2. However, whether CO2narcosis and diapause act in concert to affect reproduction remains unknown. Here, we investigated the separated and combined effects of diapause and CO2on female reproduction in queens of the common eastern bumble bee Bombus impatiens. Queens were treated with CO2 following a cold storage period (zero days, two weeks, two and four months) and were compared with untreated queens at the same timepoints for survival, colony initiation, egg-laying latency, and offspring production. We found that both CO2 and a period of at least two months in cold storage induced a transition to egg laying in gynes, and as expected, survival decreased with cold storage length. When CO2 and cold storage were combined, CO2narcosis positively affected egg laying in the earlier timepoints but its impact diminished following a longer cold storage. These data suggest that the impacts of CO2narcosis and cold storage are partially additive, and application of CO2 is effective only after a short cold storage. It further demonstrates that CO2 has complex effects on insect reproduction that are independent from diapause.

A neonicotinoid pesticide alters how nectar chemistry affects bees

Abstract Neonicotinoid pesticides in the nectar and pollen of managed crops and wildflowers contribute to the global declines of bees. These chemicals can have detrimental effects on bees' physiology, behaviour and reproduction. Floral nectar also contains secondary chemistry with its own effects on bee health. How nectar secondary chemistry may act additively or synergistically with neonicotinoids is unknown. Here, we asked how an acute exposure to a common neonicotinoid, imidacloprid (IMD) affected the longevity, immune function and behaviour of bumble bee Bombus impatiens workers maintained on diets enriched with one of three nectar secondary metabolites (NSMs; the alkaloid caffeine, the terpenoid thymol or the cardiac glycoside digoxin). A factorial design allowed us to assess the potential for additive and interactive effects of each NSM and IMD combination on multiple health outcomes. Without IMD exposure, different dietary NSMs each had positive effects on life span (caffeine), immune function (digoxin) and activity levels (caffeine, thymol), although these came with trade‐offs. A single sublethal IMD exposure overshadowed these NSM effects, and in two cases, an NSM‐enriched diet magnified the negative effects of pesticide exposure. In summary, we show that even a single acute exposure to a pesticide has the potential to reshape interactions between pollinators and plants mediated by nectar secondary chemistry. Read the free Plain Language Summary for this article on the Journal blog.

A Gland of Many Uses: a Diversity of Compounds in the Labial Glands of the Bumble Bee Bombus impatiens Suggests Multiple Signaling Functions.

Communication in social insect colonies depends on signals accurately reflecting the identity and physiological state of the individuals. Such information is coded by the products of multiple exocrine glands, and the resulting blends reflect the species, sex, caste, age, task, reproductive status, and health of an individual, and may also contain caste-specific pheromones regulating the behavior and physiology of other individuals. Here we examined the composition of labial gland secretions in females of the bumble bee Bombus impatiens, of different castes, social condition, age, mating status, and ovarian activation. We show that active queens, gynes, and workers each produce caste-specific compounds that may serve different communicative functions. The composition and amounts of wax esters, mostly octyl esters produced by active queens, differed significantly between castes, mating, and social conditions, suggesting a social signaling role. Farnesyl esters were predominant in gynes and peaked at optimal mating age (6-10days), suggesting their possible roles as sex pheromone components. Reproductive status of females and age across castes was reflected by the ratio between short- and long-chain hydrocarbons, suggesting that these compounds may serve as fertility signals. Our findings overall suggest that the labial gland composition in B. impatiens reflects different facets of female physiology. While further bioassays are required to determine the functions of these compounds, they are likely to have important roles in communication between individuals.

Proline as a Sparker Metabolite of Oxidative Metabolism during the Flight of the Bumblebee, Bombus impatiens.

Several insect species use the amino acid proline as a major energy substrate. Although initially thought to be limited to blood-feeding dipterans, studies have revealed this capability is more widespread. Recent work with isolated flight muscle showed that the bumblebee Bombus impatiens can oxidize proline at a high rate. However, its role as a metabolic fuel to power flight is unclear. To elucidate the extent to which proline is oxidized to power flight and how its contribution changes during flight, we profiled 14 metabolites central to energy and proline metabolism at key time points in flight muscle and abdominal tissues. Ultra-high performance liquid chromatography-electrospray ionization-quadrupole time of flight mass spectrometry (UPLC-ESI-QTOF MS) analysis revealed that proline is likely used as a sparker metabolite of the tricarboxylic acid cycle at the onset of flight, whereby it supplements the intermediates of the cycle. Carbohydrates are the major energy substrates, which is evidenced by marked decreases in abdominal glycogen stores and a lack of alanine accumulation to replenish flight muscle proline. The time course of fuel stores and metabolites changes during flight highlights homeostatic regulation of energy substrates and patterns of changes in metabolic intermediates within pathways. This study clarifies the role of proline and carbohydrate metabolism during flight in hymenopterans, such as B. impatiens.

Big bees spread disease: body size mediates transmission of a bumble bee pathogen.

Trait variation can have important consequences for the outcomes of species interactions. Even though some traits vary as much within species as across related species, models and empirical studies typically do not consider the role of intraspecific trait variation for processes such as disease transmission. For example, many pollinator species are in decline because of a variety of stressors including pathogens, but the role of intraspecific trait variation in mediating disease dynamics is rarely considered. For example, pollinator body size could affect pathogen transmission via differences in resistance, foraging behavior and physiology. We tested effects of body size on pollinator pathogen transmission using the common eastern bumble bee Bombus impatiens in field tents, introducing an infected "donor" microcolony of large or small workers with an uninfected average-sized "recipient" microcolony and allowing bees to forage for 9-16d. Small donor bees had nearly 50% higher infection intensity (cells/0.02 μL) than large donor bees, but large donor bees were twice as likely to transmit Crithidia bombi to recipient bees. Both behavioral and physiological mechanisms may underlie this apparent paradox. Compared to small bees, large bees foraged more and produced more feces; simulations showed that foraging and defecation rates together had stronger effects on transmission than did donor infection intensity. Thus, effects of bee size on contact rates and pathogen supply may play significant roles in disease transmission, demonstrating the multifaceted impacts of traits on transmission dynamics.

Blueberry Yields Increase With Bee Visitation Rates, but Bee Visitation Rates are not Consistently Predicted by Colony Stocking Densities.

Pollinator-dependent crops rely on the activity of managed and wild pollinators. While farm management and surrounding landscape can influence wild pollinator contributions, managed pollinator contributions may be primarily driven by their stocking densities, though this is not well studied across crops. We selected 20 southern highbush blueberry farms along two independent gradients of honey bee Apis mellifera L. (Hymenoptera: Apidae) stocking density (~1-11 hives/acre) and bumble bee Bombus impatiens Cresson (Hymenoptera: Apidae) stocking density (0 - 3 colonies/acre) ensuring that stocking densities were not correlated with farm or landscape attributes. Across farms, we observed managed and wild bee visitation rates, and measured yield estimates. Farms with greater bumble bee stocking densities had higher bumble bee visitation rates and yield estimates, but farms with higher honey bee stocking densities only received higher honey bee visitation rates at the end of bloom and did not have higher yield estimates. The main wild pollinator, the southeastern blueberry bee Habropoda laboriosa (Fabricius) (Hymenoptera: Apidae), showed higher visitation rates on organic farms and in late bloom. In general, higher visitation rates by honey bees, bumble bees, and H. laboriosa were correlated with higher yields. Our results suggest that yields are limited by bee visitation rates, and that within the stocking density ranges studied, increasing managed bumble bees, but not honey bees, increases their visitation rates. While H. laboriosa had the greatest effect on yield estimates, its activity appears to be limited by both a phenological mismatch with crop bloom and farm management.

Dufour\u2019s gland analysis reveals caste and physiology specific signals in Bombus impatiens

Reproductive division of labor in insect societies is regulated through multiple concurrent mechanisms, primarily chemical and behavioral. Here, we examined if the Dufour’s gland secretion in the primitively eusocial bumble bee Bombus impatiens signals information about caste, social condition, and reproductive status. We chemically analyzed Dufour’s gland contents across castes, age groups, social and reproductive conditions, and examined worker behavioral and antennal responses to gland extracts. We found that workers and queens each possess caste-specific compounds in their Dufour’s glands. Queens and gynes differed from workers based on the presence of diterpene compounds which were absent in workers, whereas four esters were exclusive to workers. These esters, as well as the total amounts of hydrocarbons in the gland, provided a separation between castes and also between fertile and sterile workers. Olfactometer bioassays demonstrated attraction of workers to Dufour’s gland extracts that did not represent a reproductive conflict, while electroantennogram recordings showed higher overall antennal sensitivity in queenless workers. Our results demonstrate that compounds in the Dufour’s gland act as caste- and physiology-specific signals and are used by workers to discriminate between workers of different social and reproductive status.

Effects of the Neonicotinoid Acetamiprid in Pollen on Bombus impatiens Microcolony Development.

Honey bees and other wild bee species including bumble bees have experienced population declines in recent decades. Although many stressors are implicated in bee population declines, much attention has focused on neonicotinoid pesticides, which are widely used and known to be toxic to pollinators. One neonicotinoid, acetamiprid, has been studied very little in bumble bees, despite its use on bumble bee-pollinated crops. We assessed the impacts of acetamiprid to the North American bumble bee Bombus impatiens using the microcolony model. We examined nest growth, development, and subsequent nest productivity as measured by drone production. We found that high concentrations of acetamiprid in pollen (4520 µg/kg) significantly impacted nest growth, development, and, ultimately, reproduction (drone production). We found the no-observable-adverse effect level to be 45.2 µg/kg. Overall, acetamiprid has the potential to negatively impact reproductive endpoints for B. impatiens. However, effects occurred at concentrations substantially higher than expected environmental concentrations that would be achieved when following label rates. Further work is required to assess the effects of this pesticide on B. impatiens via alternate routes of exposure and on queenright colonies. Environ Toxicol Chem 2020;39:2560-2569. © 2020 SETAC. This article has been contributed to by US Government employees and their work is in the public domain in the USA.