Like night and day: a review of nocturnal predator communities and predation in annual row crop agroecosystems

Abstract

Biological control through arthropod predation is one of the most economically important ecosystem services in agriculture. Because of this, documenting predator communities’ ecological and behavioral responses to the environment and the resultant changes to predator activity and predation are crucial to agricultural sustainability. Temporal variability in resources, environmental conditions, and arthropod behavior is increasingly recognized for its ecological importance. However, this recognition is largely focused on shifts in diurnal aspects of the ecosystem. Nocturnal predation can match or exceed diurnal predation across predatory taxa, so ignoring nocturnal predation risks overlooking species that contribute significantly to predation services. This review assembles current knowledge about nocturnal predation in annual row crops, outlines its importance, and advocates for further work in this understudied area. Comprehensive identification of predator communities is quite rare, with nocturnal communities even more woefully under-researched than their diurnal counterparts. This represents a major blind spot in entomology, especially for predation ecology, and even persists where predation is known to primarily occur nocturnally, allowing severe underestimation of pest control by nocturnal predators. The more ephemeral nature of predation and the difficulty of direct documentation preclude many passive collection methods, especially for evaluating diel activity of the predatory complex in situ. Further, changing climates may differentially affect diurnal and nocturnal predators, leading to significant impacts on predation outcomes. Both nocturnal and diurnal predators face spiking temperatures and their associated desiccation threat and phenological shifts though different activity patterns will likely alter the impact of the changing climate on these predatory complexes.

Introduction

Insect-derived ecosystem services are paramount to the success of modern monocultural row crop practices. Pollination, nutrient cycling, and biological control all rely heavily on insects, often in under-documented ways (Losey and Vaughan 2006). Though these services are all crucial to agricultural success (Perez-Alvarez et al. 2019), here we focus on biological control because of its foundational protective role for food production and agricultural economies around the world (Bale et al. 2008, Ferron and Deguine 2009, Kergunteuil et al. 2016) and its vulnerability to chemical insecticides and climate change (Thomson et al. 2010, Mwalusepo et al. 2015). Integrated Pest Management (IPM) principles recognize the ecosystem’s foundational role and emphasize the use of ecologically sound practices (eg habitat manipulation, cultural practices, and physical controls) to support biological control and plant resistance as preferred tactical priorities over chemical interventions (Karlsson Green et al. 2020). However, research time and money allocation are currently out of sync with these principles, prioritizing insecticidal research and control strategies for individual pests in isolation (Deguine et al. 2021). This leads to pest management strategies of siloed tactical modules rather than an integrated strategy (Stenberg 2017), as researchers focus on individual pests, crops, systems, or approaches without examining how they fit into a broader holistic IPM system. This approach prioritizes incremental improvements to stave off the collapse of the current unsustainable agricultural system rather than more ecology-based transformative solutions. Research that seeks true integration and alignment with the purported goals of IPM needs to establish cross-disciplinary strategies and focus on communities and systems rather than individual interactions or organisms in isolation (Stenberg 2017). Land managers and proponents of IPM must, therefore, solidify an increased understanding of biological control agent biology and ecology in future studies to better provision the changing landscape to support biocontrol agents’ survival and maintain effective population densities.

An ecologically sound understanding of resource composition (Landis et al. 2000, Dainese et al. 2019), configuration (Fahrig 2002, Langellotto and Denno 2004), connectivity (Zeigler and Fagan 2014, Uroy et al. 2021), and continuity (Haan et al. 2020) and how they influence organisms is necessary for effective management. Environmental changes occurring over years, seasons, and diel periods influence all of these factors and are critical to organism survival, fitness, and access to resources (Romero and Harwood 2010, Welch and Harwood 2014, Schellhorn et al. 2015, McMunn and Hernandez 2018, Iuliano and Gratton 2020, Spiesman et al. 2020). Though the importance of these temporal factors is increasingly recognized, relatively little is known about nocturnal ecology. This oversight creates a worrisome blind spot given that nocturnal species, resources, and processes comprise much of the biodiversity within a given landscape and their ecosystem functions. Understanding the effects of organismal access to resources in space and time provides a foundation for ecological research (Wiens et al. 1993) and therefore holds a great deal of promise for building sustainability through agroecological intensification (Landis et al. 2000, Lovell and Johnston 2009, Landis 2017). But the dearth of research on nocturnal ecology limits our understanding of important influences on ecosystem functioning and potential conservation improvements. In agriculture especially, seeking to understand nocturnal resource landscapes, biodiversity, and ecosystem services can improve our understanding of the population dynamics and ecosystem services of beneficial arthropods, along with the pests they consume.

Environmental and resource changes across years (Macfadyen et al. 2015, Bosem Baillod et al. 2017), seasons (Ximenez-Embun et al. 2014, Bertrand et al. 2016), and days can influence predatory activity, predation amount, and overall predation ecology on a landscape. Perhaps largely due to humans’ diurnal lifestyles, the majority of arthropod predation is measured diurnally or is quantified without regard to diel timing (Gaston 2019). Fewer studies investigate nocturnal predation, though it can match or exceed diurnal predation across predatory taxa (Cottrell and Yeargan 1998a, 1998b, Pfannenstiel and Yeargan 2002, Pfannenstiel 2004, 2005, Myers et al. 2020); and globally, many insect taxa are more active nocturnally (Wong and Didham 2024), including 77% of Lepidopterans and 60% of Coleopterans (Hölker et al. 2010) for which such information is available. Uncovering these nocturnal behavior patterns could reveal important ecological factors influencing arthropod behavior in general and predation specifically. Even diurnal and crepuscular activity patterns can provide important insights into temperature ranges, the influence of humidity, light intensity, actual or perceived predation exposure, or niche differentiation. Evaluating and reporting diel activity and predation patterns can provide valuable information about the ways that environmental factors alter pest behavior and predation services within the agricultural landscape.

From the human perspective, benefits ascribed to arthropods are understandably appreciated only as much as their corresponding documentation allows. In other words, the “value” of any given insect is calculated by the tangible benefit the species provides to humans within its specific landscape (Losey and Vaughan 2006). Within this framework, for example, we measure pollination based on seed set and crop yield (Chen et al. 2024, Heuel et al. 2024); nutrient cycling by the amount of specific nutrients or soil characteristics in the landscape (Culliney 2013, Sagi and Hawlena 2021); and parasitism by rearing out field-collected pests and observing evidence left by parasitoids (eg aphid mummies or pupal exuviae on caterpillar corpses, desiccated host cadavers) (Müller et al. 1999), or DNA barcoding (Miller et al. 2021), among other methods. In contrast, predation is marked by a lack of pests and pest damage more than by the presence of any easily measurable residue in the environment, so assigning value to predation is complex (Tschumi et al. 2018). Gut content analysis and other DNA-based tools can help construct trophic webs and predatory relationships (Krehenwinkel et al. 2017, Paula and Andow 2023), although these techniques also have their weaknesses. Even these tools, while valuable, are restricted mostly to qualitative presence–absence evaluation, though advances are being made in this area (Andow and Paula 2023), especially with rate quantification (Uiterwaal and DeLong 2020). The difficulty of assigning value to predation services presently necessitates direct documentation through visual observation. This visual documentation, whether in person or recorded in still photography or video, is crucial to establishing predatory relationships between agricultural pests and their predatory complexes (Grieshop et al. 2012) and quantifying the relative contribution of each of the predators. Accurately evaluating the scope of contributions made by predation to agricultural food, feed, fiber, and fuel can highlight the importance of this easily overlooked service and the need for additional research on how management can be best integrated with the agricultural landscape.

This review assembles current knowledge on nocturnal arthropod predation in agroecosystems and discusses the implications of this knowledge for IPM, conservation, and future applications under climate change. This knowledge is examined in context with other temporal factors (eg seasonal and diel activity partitioning) that interface with nocturnal predation. We examined literature on arthropod abundance, population structure, and biological control services in regard to environmental, behavioral, and biological characteristics. We explore how changes in nocturnal—and to a lesser extent diurnal—environment and resources influence the abundance, diversity, behavior, and biological control potential of predatory arthropods.

Discussion

Importance of Nocturnal Predation

Nocturnal predation has been shown to be comparable or even exceed diurnal predation in systems that have been examined in the limited literature. Early studies by Vickerman and Sunderland (1975) and Brust et al. (1986) demonstrated with a combination of gut content testing and visual observations that nocturnally active predators could play a pivotal role in pest mortality. The use of sentinel prey has been very successful in determining prey consumption and the makeup of predator complexes in various crop systems. For Helicoverpa zea Boddie in Kentucky, United States, predation was context-dependent with respect to crop system (sweet corn vs soybean), season (July vs August), and diel pattern (diurnal vs nocturnal), though the dominant predators were consistent from year to year within these contexts (Pfannenstiel and Yeargan 2002). In the same location (Kentucky), in sweet corn, diel predation and the arthropods responsible for mortality varied within corn depending on the target prey (H. zea or Coleomegilla maculata De Geer eggs), predator stage, the presence of particular weeds within corn fields, or the presence of pollen (Cottrell and Yeargan 1998a, 1998b). Weber et al. (2008) demonstrated that previously unknown nocturnally active predators were very active in multiple important cropping systems, including potatoes, cotton, soybean, and corn. Studies on the mortality of Monarch (Danaus plexippus L.) butterfly eggs and immatures found that 10 taxa representing 8 orders of arthropods attack them. Each exhibited a distinct diel predation pattern, although overall predation was greater nocturnally than diurnally (Myers et al. 2020). Nocturnal predators and predation are likely very important for agricultural pest control, but what little we know also indicates a complex and diverse group of predators reacting to a suite of under-researched ecological influences.

Predator Diversity and Overlooked Nocturnal Natural Enemies

Identifying all members of a predator community can provide land managers with comprehensive and accurate information on the species preying on each agricultural pest and ensure conservation efforts can be extended to predators that provide this control. Species diversity in insect communities has long been recognized to improve ecosystem services. Whether this is due to effective niche partitioning, ecological redundancy, or other processes, complementary species usually increase the efficacy of biological control (Snyder et al. 2006). Western corn rootworm, Diabrotica virgifera virgifera LeConte, has a complex, distinct community of predators associated with diurnal predation versus nocturnal predation (Lundgren et al. 2009). Individual predator species that predate more nocturnally than diurnally include Dicyphus hesperus Knight (Hemiptera: Miridae; VanLaerhoven et al. 2003). While Pterostichus melanarius (Illiger; Coleoptera: Carabidae) showed greater predator activity nocturnally than diurnally, ground cover increased the amount of relative activity and spread their activity over a greater number of hours (Chapman et al. 1999). Additionally, overall predator activity was more even across diel periods in systems with lower management disturbance (Lundgren et al. 2006), suggesting the strongly uneven diel patterns of predator activity in agroecosystems may result from the disturbance in annual row crop production rather than a strong intrinsic result of predator biology alone, at least for ground-dwelling arthropods. A common theme among the studies referenced here is that the identification of nocturnally active predators revealed taxa that were previously not believed to be important. Altogether, it is clear that failing to document nocturnal predators and predation risks ignores predators that provide significant pest suppression in our agricultural systems.

Comprehensive Predator Complex Identification

Comprehensive identification of important predator complexes has been completed on only a very small fraction of agricultural systems. Even in pest systems that have been studied for decades, full characterization of predatory complexes is rare (but see, Whitcomb and Bell [1964] for a comprehensive look at predators in cotton in Arkansas, United States; Cottrell and Yeargan [1998a, 1998b] and Pfannenstiel and Yeargan [2002] for corn and soybean in Kentucky; Pfannenstiel [2004, 2005] for lepidopteran eggs in cotton in South Texas, United States; Lundgren et al. [2009] for coleopteran eggs in corn in South Dakota, United States). This is particularly problematic if a significant amount of predation occurs nocturnally. For example, significant mortality contributed by nocturnal spiders in multiple Texas cropping systems would be seriously underestimated if only diurnal predation by jumping spiders is taken into account (Pfannenstiel 2008). This underestimation of spider predation was also noted in Monarch butterfly (D. plexippus L.) egg predation (Myers et al. 2020). Nocturnal observations may also be critical when novel predators, such as the cockroach Blattella asahinai Mizukubo, expand their range into new regions and agricultural systems (Pfannenstiel et al. 2008). Gut content analysis found that more polyphagous predators fed on aphids at night than during the day (Vickerman and Sunderland 1975). Recent video surveillance in corn identified distinct diurnal (Coccinellids and Anthocorids) and nocturnal (Opiliones and Araneae) predators (Petersen and Woltz 2015), again illustrating high nocturnal predator activity, especially in arachnids. Passive arthropod sampling techniques are widely used, and if deployed throughout the diel period, can provide valuable insights into nocturnal activity. However, direct comparisons between diurnal and nocturnal activity with passive methods can be difficult because of differences in attractant modalities (eg color lures, light traps; Fajemisin et al. 2023) and differential day/night temperature effects on arthropod behavior (McNamara Manning and Bahlai 2022). Ultimately, nocturnal activity must be validated with direct observation methods.

The Nocturnal Ecology Research Gap

Publications, conference sessions, and formal structured discussions on the night-time ecology of many systems are rare relative to their diurnal counterparts (Gaston 2019). The number of studies documenting insect diel patterns has remained low but steady at 7 to 12 per 5-year period across the last 70 years, with a brief spike in the early 2000s (Wong and Didham 2024). Considering that overall publications increased from 1.2 million to 3.3 million in the decades between 2003 and 2022 (Science and Engineering Indicators 2023), such low numbers illustrate the lack of, and even declining (relative to overall publication numbers), attention paid to nocturnal ecology research. Existing studies often report specifics of individual species rather than predator complexes or ecological communities (Gaston 2019). Such focused work fails to characterize ecological communities but may reveal specific and valuable details about biocontrol for individual predator–prey pairs (Weber et al. 2008). In any case, the lack of information represents understudied avenues of pest management by important but cryptic predators through interactions with biotic factors and abiotic environmental conditions.

Biotic Influences on Diel Activity Patterns

Biotic factors—such as sensory capacity, plant–insect interactions, and behavior—influence diel activity patterns. Volatile blends emitted by plants wounded by herbivory can preferentially attract some generalist nocturnal predators such as Doru luteipes Scudder (Dermaptera: Forficulidae) (Naranjo-Guevara et al. 2017). Such insect–plant interactions are well-known to exist in diurnal arthropod species (Paré and Tumlinson 1999, Kaplan 2012), and olfaction may prove to hold equivalent, or even greater, importance in nocturnal systems where visual prey searching may be less effective. Vibration cues used in prey searching may be similarly important (Pfannenstiel et al. 1995, Brownell and van Hemmen 2001, Roberts et al. 2007, Virant-Doberlet et al. 2019), especially for spiders through their abundance of specialized sensory structures and behavioral attunement to substrate vibration (Virant-Doberlet et al. 2014). Indeed, prey searching often focuses on cryptic or otherwise hidden prey items, even in diurnal species, and the difficulty of visual searching has been documented for many natural enemies (Paré and Tumlinson 1999), underscoring the importance of non-visual cues for prey localization. Many different factors may impact the diel activity patterns and resultant behavior of nocturnal predators; it is therefore important to investigate many different potential influences in future work in this area.

Even without direct, identifiable influence from environmental factors, diel partitioning of overall predation behavior may be altered by behavioral differences within natural enemy complexes or even within individual species. Some predators show no specific diel activity patterns or alter their activity based on unidentified factors (Kiritani et al. 1972, Luff 1978), which may indicate that other factors, such as prey availability, provide the dominant influence on this behavior as observed in mammalian systems (Botts et al. 2020). However, factors such as sex can influence diel activity within arthropod species. For example, activity peaks for some male carabids lag behind conspecific females by around 1 h (Luff 1978). Since temperature and sunlight intensity change throughout the diel period, differences in thermoregulatory behavior can yield different activity period peaks. Characterizing pest and predator diel activity patterns can provide valuable foundational information to guide management strategies and their timing to optimize efficacy. The relationship between temperature fluctuations and diel partitioning could have much ecological relevance to successful biological control in our changing climate.

To integrate services from the nocturnal predator community into IPM theory and practice, we first need to establish how much, if any, nocturnal predation is occurring in many important crop systems. Current knowledge indicates that nocturnal predation activity is comparable to diurnal predator activity for at least some systems (Petersen and Woltz 2015). For instance, nocturnal predation of lepidopteran eggs can account for significant mortality in cotton, corn, and soybean, while each predator displayed species-specific activity patterns (Cottrell and Yeargan 1998a, 1998b, Pfannenstiel and Yeargan 2002, Pfannenstiel 2004, 2005). An investigation into the spatial, seasonal, and diel partitioning of aphid predation in alfalfa found that different predator species were most active during specific seasons and diel periods, though predation amount was not tightly tied to predator field abundance in all cases (Ximenez-Embun et al. 2014). In another study, the highest numbers of both syrphid larvae and polyphagous arthropods were observed in cereal crops between 21:00 and 06:00 h (Vickerman and Sunderland 1975). These examples suggest that nocturnal predation can be comparable to or even greater than diurnal predation in similar landscapes.

Intraguild Predation

Within predator complexes and communities, intraguild predation is a significant concern for biological control efficacy. Intraguild predation conflict and resource competition are increased in spatially simplified landscapes as the lower complexity increases predators’ interaction frequency (Perez-Alvarez et al. 2019). Frequent predator interactions provide increased opportunities for intraguild predation, which can reduce overall pest suppression through added predator mortality and dilution of predation pressure on pests. Therefore, predator activity-density that is distributed more evenly across the diel period likely reduces the number of predatory interactions and thus predator–predator conflict. Time and space partitioning thus may be critical for natural enemy communities and pest suppression (Snyder et al. 2006). For instance, video surveillance of soybeans showed that coccinellid larvae, carabids, staphylinids, and syrphids were active diurnally only, greatly reducing their exposure to predation risk from nocturnally active spiders, Opiliones, and neuropterans (Petersen and Woltz 2015). However, when the intraguild predation is due to cannibalism, it may be impossible to escape over the diel period as observed in corn with C. maculata (Cottrell and Yeargan 1998b, 1998a). Indeed, diel-partitioned activity may even reflect a response to predation risk as we see in aquatic insects partitioning foraging time (Johnson 1995). For some predators, the balance between predation risk and their own foraging may be an important determinant of movement and activity patterns (Botts et al. 2020), especially where competitors overlap in diel activity (Johnson 1995). Lightscapes and their effect on the ecology of fear have been studied in nonarthropod marine predators (Beltran et al. 2021) and African lions (Packer et al. 2011), with the visibility or invisibility afforded by light penetrance determined to be a significant factor in risk–reward calculations for prey. Within this context, determining the diel activity patterns of predatory complexes can inform our understanding of the intraguild predation potential within these systems.

Abiotic Influences on Diel Activity Patterns

Insect predator diel activity patterns likely respond to a suite of environmental conditions, including temperature, humidity, light intensity, shelter, and resource niche availability. In exothermic organisms like arthropods, humidity and temperature are primary concerns (Mellanby 1939), especially for those with higher movement requirements. Temperature thresholds were shown to be crucial to the activity patterns of cursorial carabid species in southern Norway, and nocturnal activity patterns helped these predators avoid both desiccation and predation (Ottesen 1985). The greater microclimatic changes found in upper rainforest canopies (Parker 1995) can increase faunal turnover between day and night in these regions (Basset et al. 2003); and though arthropod activity was higher overall diurnally, these numbers come mostly from flying herbivorous arthropods, dung beetles, and parasitoids (Davis et al. 1997, Compton et al. 2000, Basset et al. 2003), not predators. Aridity, humidity, and elevation influence the proportion of nocturnal versus diurnal mammal species present in a region (Bennie et al. 2014). Very high humidity and dewfall can create a significant challenge for nocturnal arthropods, requiring specific adaptations to manage (Basset et al. 2003). Nocturnal dewfall poses a direct drowning danger and can increase movement cost due to added weight from wetting or present thermoregulatory challenges for wet arthropods. Relatedly, irrigation can lower predator abundance, including that of the most commonly collected spiders (Araneae: Thomisidae), and diurnal predation rates in vineyards (Melloul et al. 2024). Mosquitoes shed water droplets actively (Dickerson and Hu 2014), and behaviors to manage these challenges are likely ubiquitous, though these bear associated metabolic costs. Conversely, beneficial humidity levels can increase predation activity in some carabid ground predators due to plant microclimate and maintenance of humidity levels (Chapman et al. 1999). However, despite this higher predation activity in more humid environments, light intensity itself was also an important influence on predation behavior, as these predators showed a greater preference for lower light intensity under dense cover in the daytime, while no location preference was present in the absence of shade. Arthropod communities can be highly time-structured, with characteristic community subsets active in crepuscular hours and distinct nocturnal and diurnal groups (Pfannenstiel and Yeargan 2002, Petersen and Woltz 2015, McMunn and Hernandez 2018). Additional work in the biogeography of temporal activity patterns can reveal information about how communities may change under changing climatic conditions. In contrast, some data in mammalian systems indicate that prey availability is more predictive of diel partitioning than climatic conditions (Botts et al. 2020). These few examples point to the complexity of nocturnal ecology and the wide array of ecological processes that may be elucidated through the study of nocturnal predation.

Nocturnality and the Changing Climate

Arthropod biodiversity loss and population decline due to anthropogenic factors are well documented (Shortall et al. 2009, Hallmann et al. 2017, Leather 2018, Sánchez-Bayo and Wyckhuys 2019, Wagner 2020). Large changes in arthropod populations and phenology of agriculturally important species can challenge food security (Vanbergen and the Insect Pollinators Initiative 2013), agricultural sustainability (Cock et al. 2013, Sharma and Dhillon 2020), and stakeholder solvency (Schuurman and Ker 2025) under changing climatic conditions. Rising mean temperatures will be a major challenge, but related changes to aridity zones, temperature peaks and variability, humidity, solar radiation, and other factors will also likely threaten arthropod populations. Cooler temperatures, lower temperature variability between habitats and landscapes, increased humidity, and protection from solar radiation are all benefits of nocturnality (Daily and Ehrlich 1996). Nocturnality may offer limited buffering from climatic challenges that may be important to the continued provisioning of important ecosystem services. Regardless, nocturnal arthropods likely will be differently impacted by climate change relative to their diurnal counterparts.

Predatory taxa are diverse, and their individuality will interact uniquely with environmental conditions and climate challenges. It is imperative to foster natural enemies that can persist within agricultural landscapes and provide significant predation to maximize pest control potential and support remaining ecosystem services. Therefore, the continued success of agricultural pest management and crop protection relies upon identifying key predators that contribute to crop protection—especially those that are more easily overlooked due to nocturnal activity or cryptic behavior—and evaluating their potential responses to climate change. Climatic norms are already shifting, presenting novel challenges for predators, the protections nocturnality can present may be crucial to the survival of predatory complexes in agroecosystems. It is critical to dedicate research toward understudied species, interactions, and behaviors that occur nocturnally in our agricultural and natural landscapes.

Conclusion

The type of crop production and plant communities, the biology of arthropod pests, their environmental niches and resource needs, intraguild predation, seasonality, and diel partitioning all alter the performance of pest suppression in agriculture. Investigating the differences and similarities between predator communities across diel periods can help determine optimal conditions and niches for these predators, and, ultimately, how best we can support their survival in the agricultural landscape and beyond. Understanding what environmental conditions may alter which biocontrol agents dominate the system and provide the bulk of predation services can help customize and integrate pest management into the ecological context of the agricultural field. Likewise, investigating whole complexes and communities of predators and their seasonal and diel activity peaks can provide a more comprehensive view of predatory activity. Failing to adequately identify and measure all sources of predation can leave agricultural stakeholders at a loss to understand the scale and character of their pest management challenges, leading to both a lack of protection for important, but cryptic, biocontrol agents and an inability to accurately evaluate and respond to potentially damaging pest populations. Further, the current lack of knowledge and research effort dedicated to nocturnal aspects of the agricultural system leaves us underprepared to support predation services and predator biodiversity in the changing climate.

Author Contributions

Hannah E. Stowe (Conceptualization [lead], Investigation [lead], Writing—original draft [lead]), Robert Pfannenstiel (Investigation [supporting], Writing—review & editing [equal]), John Ruberson (Supervision [equal], Writing—review & editing [equal]), and Julie A. Peterson (Funding acquisition [equal], Resources [equal], Supervision [equal], Writing—review & editing [equal])

Funding

This research was supported by the US Department of Energy’s Office of Critical Minerals and Energy Innovation (CMEI) under the Bioenergy Technologies Office Bio-Restore Program (EXCHANGE: Expanding the Conversion of Habitat in the Northern Great Plains Ecosystem, award number DE-EE0009279).

Conflicts of Interest

None declared.