Stink bugs (Hemiptera: Pentatomidae) have emerged as an important pest species complex in soybean production systems across the southeastern United States. Changing cropping practices and climatic conditions are reshaping the stink bug communities in the region. Understanding community differences will be important to tailor integrated pest management programs sensitive to variation in species composition. In this 3-year study (2022-2024), we characterized stink bug diversity and abundance in 154 commercial soybean fields distributed across 3 soybean-producing ecoregions (Coastal Plain, Piedmont, and Mountains) in 2 southeastern states, North Carolina and Virginia. Standardized 25-sweep samples were collected at 10 locations per field during the soybean reproductive stages. Field-level samples were used to evaluate the probability of exceeding the recommended economic threshold for damage. We observed differences in stink bug community composition and spatial variation in the distribution of common stink bug species across the ecoregions. Additionally, the risk of soybean fields exceeding the recommended economic threshold differed across the ecoregions, with the Mountain region at the greatest risk. This result highlights the importance of regionally specific scouting and management recommendations that are sensitive to species composition differences. This work also provides a benchmark to assess range shifts of stink bug species in North Carolina and Virginia.

Dragonflies and damselflies are exposed to various anthropogenic stressors in the aquatic-terrestrial ecosystem, which can affect their development and fitness. The symmetry of their wings, shaped during the aquatic larval stage, can serve as an indicator of environmental stress during development. Recent advances in computer-vision now provide the opportunity to standardize and enhance the precision of 2D assessments of entire wings, including many structural parameters, enabling a more reliable comparison of the effects of multiple anthropogenic stressors. We investigated the effect of 3 anthropogenic stressors on the fluctuating wing asymmetry of the damselfly Coenagrion puella: (i) Exposure to the agricultural insecticide chlorantraniliprole in a climate chamber experiment, (ii) alteration of the aquatic community with the mosquito control agent Bti (Bacillus thuringiensis israelensis), and (iii) altered hydrological regimes, both of which were applied in a floodplain mesocosm experiment in a full 2-factorial design. We found changes in wing size and several asymmetry parameters in response to the insecticide and altered hydrological regimes, whereas Bti treatment increased the number of cells in front wings. Our results show that damselflies' wing morphology and symmetry can be affected by anthropogenically induced stress in aquatic ecosystems. The intensity of stressor effects varied across treatments, with altered hydrology causing the strongest changes in wing size and asymmetry.

Evolution of resistance within insects to pest control has resulted in changes to the organism's morphotype, including changes in wing shape. Both geometric morphometric and finite element method (FEM) were used to examine wing changes in Helicoverpa zea sampled from 4 different Bt corn treatments in North and South Carolina, United States. The 4 treatments were pure-stand non-Bt corn (treatment 1); pure-stand Bt corn with 2 toxins (Cry1Ab and Cry1F; treatment 2); pure-stand Bt corn with 3 toxins (Cry1Ab, Cry1F, and Vip3A; treatment 3); and seed blended Bt corn with 80% containing 3 toxins (Cry1AB, Cry1F, and Vip3A) and 20% having no toxins (treatment 5). Geometric morphometric analyses revealed significant wing shape differences in both female and male moths were driven by moderately selected moths (treatments 2 and 5). Male and female moths, especially from treatment 5, had longer and more slender forewing shape conducive for longer distance flight. FEM modeling of the flight potential in both male and female H. zea revealed that the highest wing elastic deformation values for wind speed, indicating the most impact on wing structure, occurred for treatment 2> treatment 1> treatment 3> treatment 5. Wing elastic deformation was significantly more pronounced in female than male moths. In conclusion, we found that one generation of selection on Bt corn in the field could induce H. zea wing phenotypes more conducive for potential long-distance dispersal and should be further investigated by directly testing the impact on migratory flight. Our study contributes to the growing body of evidence that selection of H. zea on Bt crops may influence adult dispersal behavior.

Environmental disturbances have become increasingly frequent in the Amazon region. This study evaluated the potential bees of the Euglossini (Hymenoptera, Apidae) as bioindicators of environmental quality across 3 forest types-native, regenerating, and degraded-and assessed mercury (Hg) contamination in the biomass of Eulaema cingulata. Sampling was conducted between March 2021 and May 2023 in the southern portion of the Brazilian Legal Amazon. A total of 362 males euglossine were collected, representing 29 species: 177 individuals in native forest (22 spp.), 104 in degraded forest (20 spp.), and 81 in regenerating forest (23 spp.). Euglossine abundance differed significantly among forest types and varied in the interaction with seasonality. These results indicate that forest conservation status influences the structure of euglossine assemblages. Based on our findings, species such as Eufriesea ornata, Euglossa ignita, Euglossa orellana, Eulaema bombiformis, and Exaerete frontalis are more abundant in conserved forest environments. Although environmental mercury contamination was confirmed in soil and plant samples, Hg was not detected in Eulaema cingulata biomass. Nevertheless, further studies on mercury bioaccumulation in other euglossine species are warranted, given the persistent anthropogenic pressure in the southern Amazon.

The maize caterpillar, Mythimna loreyi (Duponchel, 1827) (Lepidoptera: Noctuidae), is an important migratory pest for agricultural production in Asia, but its flight performance remains poorly understood. Here, we utilized a computer-monitored flight mill system and a stroboscope to assess how adult age, sex, temperature, and relative humidity affect the flight capacity of M. loreyi. The results indicated that the flight ability of M. loreyi was most highly developed in 2-day-old adults and decreased significantly with age. Two-day-old adults under conditions of 24 °C and 80% relative humidity throughout a 12-h scotophase recorded a total flight distance of 23.5 ± 2.8 km for males and 27.2 ± 2.6 km for females, suggesting that M. loreyi has a strong potential for long-distance migration. Temperature and relative humidity had significant effects on the flight performance of M. loreyi, with the maximum flight capacity in the range 20 to 28 °C and 50% to 85% relative humidity. In addition, the wingbeat frequencies of M. loreyi adults ranged from 22.6 to 57.6 Hz and 18.6 to 56.8 Hz among different age groups and temperatures. The highest wingbeat frequency (46.0 ± 0.8 Hz) was recorded for 6-day-old moths. Wingbeat frequency increased with temperature, with maximum (47.0 ± 0.6 Hz) recorded at 36 °C. Wingbeat frequency of male moths was significantly higher than that of female moths. These findings provide a foundation for understanding M. loreyi's migration behavior and can guide the improvement of regional monitoring strategies.

Previous studies investigating the relationship between landscape composition surrounding a crop, and either plant pathogen vectors or vector-borne plant pathogens in the crop, have not observed consistent relationships, and no quantitative synthesis of the current literature has been conducted. We conducted a meta-analysis of 289 published effect sizes from 28 studies to better understand the relationships between landscape composition and plant pathogen vectors or vector-borne pathogens, while considering a series of biological, ecological, and environmental factors that may contribute to variation in the relationships. We found that vector and vector-borne pathogens were positively associated with landscape composition metrics, including the percentages of the landscape surrounding the study areas that were crop, non-crop, and natural habitat but not with habitat diversity. Vector host plant specialists exhibited a significant positive association with various landscape composition metrics, while host plant generalists did not, supporting the idea that specialists are more dependent upon specific host landscape features, whereas generalists have hosts that are generally more abundant across various landscapes. Measurements of both abundance and incidence of pests exhibited significant positive associations with landscape composition metrics. For both persistent and non-persistent pathogens, the positive association between pathogens and landscape composition became stronger at larger spatial scales (500 to 10,000 m). This meta-analysis demonstrated that increasing the percentage of crop, non-crop, or natural habitat within a landscape can increase vectors or vector-borne pathogens in the crop. However, the specific landscape feature that contributes to increased pest abundance or incidence will depend on the crop-pest system.

The soybean aphid, Aphis glycines Matsumura, is a major pest that can significantly reduce soybean yields during heavy infestations. Planting resistant varieties is essential for managing this pest, requiring effective breeding and screening. In the United States, Dowling is resistant while Williams 82 is susceptible to A. glycines. This study assessed A. glycines from Harbin, China, feeding on soybean varieties Dowling, Williams 82, Shennong 9, and line P 3 under controlled conditions. Results showed that A. glycines thrived on Dowling and Williams 82, with no significant differences in longevity, oviposition, or fecundity. Line P 3 showed greater resistance to A. glycines than Dowling, with shorter adult longevity and lower fecundity. Shennong 9 was more susceptible than Williams 82, exhibiting longer adult longevity and higher fecundity. P 3 may serve as a valuable resource for breeding resistant soybeans, while Shennong 9's susceptibility could aid in control strategies. These results are crucial for developing A. glycines-resistant soybean varieties.

Rhynchophorus palmarum, an invasive palm pest in San Diego County California, has killed thousands of Phoenix canariensis. Over July 2016 to December 2022, this study tracked the population phenology of R. palmarum. Trapping data, derived from the capture of 8,262 weevils, of which 65% were female, indicated strong and predictable seasonal patterns in adult weevil activity, with trap captures increasing after March, peaking in July, before declining steadily towards December. Approximately 80% of weevils were trapped between April and October. This finding has important implications for the timing of management practices. Frond pruning should be done over November to March when weevil flight activity is low, and prophylactic insecticide applications should be made in March and June prior to increased weevil flight activity in April and July. Temperature and day length were strongly correlated with weevil capture rates, while precipitation, wind speed, and relative humidity were not. In urban areas over a 7-year survey period, August 2016 to August 2023, palm mortality rates, based on observations of 521 palms, indicated that 68% were killed. Drone surveys of 637 wilding P. canariensis in the Sweetwater Reserve exhibited a 73% rate of mortality over August 2016 to August 2023. Strong cardinal effects were observed for palm mortality in urban areas with west and east quadrants exhibiting higher rates of mortality in comparison to palms in north and south quadrants. In urban areas, weevil killed palms were removed on average, after 400 days, at an estimated average cost of $2,861 per palm.

When sap-feeding insects invade ecosystems, they create novel resource subsidies by exposing previously unavailable resources to resident consumers. Spotted lanternfly, Lycorma delicatula (White), is an invasive phloem-feeding planthopper native to Asia that has spread across multiple US states since its 2014 detection in Pennsylvania. It heavily feeds on tree-of-heaven, Ailanthus altissima (Mill.) Swingle, an invasive tree naturalized across the United States that previously lacked sap-feeders. During feeding, L. delicatula excretes honeydew and creates sap-exuding wounds, providing carbohydrate resources. Here, we document invertebrates consuming these subsidies in southeastern Pennsylvania from June to October 2021. At 43 sites sampled 3 times, we measured L. delicatula biomass via circle trunk traps and recorded 1,576 feeding observations through visual surveys. These observations were made up predominantly of Hymenoptera (78.0%) and Diptera (19.5%), with smaller proportions of Coleoptera (0.76%), Lepidoptera (0.44%), Hemiptera (0.44%), Orthoptera (0.38%), Opiliones (0.38%), and Stylommatophora (0.06%). Among Hymenoptera, we identified 33 species (29 native, 4 introduced) from 13 families, including key pollinators and parasitoids. The invasive wasp, Vespa crabro, was abundant and exhibited aggressive behaviors toward native consumers, including pollinators. Using redundancy analysis, we tested whether spatiotemporal variation in L. delicatula biomass explained the composition of honeydew-feeding Hymenoptera compared to other environmental factors. Lycorma delicatula biomass was the strongest predictor of Hymenoptera community composition, with temperature, landscape-scale impervious surface, and site-scale vegetation structure also contributing. The L. delicatula invasion has created novel resource subsidies for many invertebrates and altered temporal dynamics of Hymenoptera, with potential cascading effects on pollination and biocontrol ecosystem services.

One of the main challenges in improving agricultural productivity is the prevalence of pests and diseases, which are highly sensitive to extreme weather conditions. The interaction between weather patterns and pest infestations significantly affects crop yield. Traditional statistical methods often struggle to capture the complex temporal and geographical dynamics of these interactions. However, employing multivariate cointegration has proven valuable for estimating such interactions and quantifying the extent to which various environmental conditions influence pest populations. The study further investigated impulse response functions, which revealed substantial impacts of temperature and relative humidity on pest populations through unit standard deviation shocks to endogenous variables. Specifically, this research examined the dynamic causal relationships between major pest occurrences and environmental variables in 3 groundnut-growing states of India-Andhra Pradesh, Gujarat, and Tamil Nadu, using cointegration and Vector Error Correction Model techniques. The analysis incorporated key environmental variables, including temperature, relative humidity, and rainfall. Results from the Johansen test indicated a strong long-term equilibrium relationship between pest populations and climatic conditions, confirming the presence of at least one cointegrating vector at the 5% significance level. Granger causality tests further revealed that temperature and relative humidity had a unidirectional causal influence on the pest occurrence. Additionally, impulse response analysis further revealed that shocks to temperature and relative humidity produced significant and persistent effects on pest incidence over time.

Artificial light at night (ALAN) can disrupt circadian rhythms and phenology for lepidoptera since photoperiod is a dominant cue for their life cycles. The goal of this study was to discover how ALAN exposure affects the timing of caterpillar development into chrysalis and metamorphosis into a butterfly. The painted lady butterfly (Vanessa cardui) frequents Texas from spring through fall. For this project, commercially sourced V. cardui caterpillars were used to study effects of ALAN in controlled indoor conditions, at a constant temperature of 23 °C. Throughout October 2020, April 2021, October 2021, and March 2022, caterpillars were exposed to 0, 9.5, 17.5, or 24 h of 300 lux white light emitting diode (LED) lights, and the days until chrysalis formation and butterfly emergence were observed. The 17.5 and 24 h ALAN light cycles caused butterflies to emerge 1 to 3 days faster than 9.5 h exposure. V. cardui development was expected to be faster under blue versus orange LED lights as their photoreceptors are more sensitive to blue wavelengths. This was tested in July through September of 2022 with exposure to 24 h white, blue, or orange LEDs versus no ALAN. Orange LED exposed butterflies emerged a day or 2 slower than blue or white LED exposed ones. Studies in 2023 with 12 h ALAN from white, blue, or orange LEDs yielded similar results, and hemolymph melatonin was reduced by blue LED exposures. Therefore, orange ALAN seems to be less disruptive to V. cardui metamorphosis than blue or white ALAN.

Temperate-zone Geometridae moths, active across seasons, offer an excellent model for investigating how related species respond to varying environmental conditions, particularly photoperiod-a major Zeitgeber regulating biological oscillators. In this study, we examined the daily cycle of sperm release from the testes in 9 geometer moth species, including univoltine and bivoltine taxa, as well as diurnal and nocturnal species. We found that sperm release into the upper vasa deferentia differs consistently between day-flying and night-flying species. Moreover, we observed marked differences in the diel regulation of sperm release between spring and summer generations of the same species. Experimental evidence suggests that these intergenerational differences are photoperiod-dependent. Further manipulation confirmed that a long photoperiod not only abolishes rhythmic sperm release but also significantly reduces the number of eupyrene sperm bundles transferred into the vasa deferentia. This is the first demonstration, under near-natural conditions, of photoperiodic regulation of a physiological rhythm in a peripheral organ via its suppression. These findings underscore the importance of environmental timing cues in reproductive physiology and provide new insights into the temporal plasticity of insect reproductive systems. Importantly, they also highlight the potential for integrating agro-chronobiological knowledge with mechanistic studies of temporal regulation in insect pests. Finally, this work adds to our understanding of how peripheral oscillators may be shaped by selective pressures in closely related species occupying distinct ecological niches, where differences in the timing of life-history processes serve as key axes of divergence.

In the years immediately following its introduction in 1986, the Russian wheat aphid Diuraphis noxia (Kurdjumov) became a significant pest of wheat in the western United States. In recent years, however, there have been few reports of economically damaging populations and lower numbers of Russian wheat aphid collected in suction traps. Here, we present evidence that the existing natural enemy complex may significantly reduce Russian wheat aphid populations even if no single species can be shown to be highly effective. In this study, we used 3 exclusion cage treatments (fully caged, partially caged, and uncaged plots) to explore the effects of the existing natural enemy complex on Russian wheat aphid populations in winter wheat in 3 fields across a north-south gradient in eastern Colorado: Fort Collins (northeastern Colorado), Akron (eastern Colorado), and Lamar (southeastern Colorado). Natural enemies were collected and identified. Fewer aphids and symptomatic wheat tillers were found in the uncaged treatment and partially caged treatments than in the caged treatment, which excluded the possibility of natural enemy attack on aphids, suggesting that natural enemies were responsible for suppressing Russian aphid populations in the open cage treatments. Predators were collected on both early and later growth stages of wheat, whereas parasitoids were found only on the later growth stage. Together, these findings suggest that the natural enemy complex is responsible for reducing Russian wheat aphid abundance among different dryland agroecosystems and climatic conditions.

Multivoltine insects, those having more than one generation per year, often use daylength as a cue for terminating reproduction and entering diapause prior to the onset of winter. In a common garden experiment in Corvallis, Oregon, USA (44.6°), we compared voltinism and impacts of the loosestrife leaf beetle Galerucella calmariensis, a classical biological control agent for the wetland weed purple loosestrife (Lythrum salicaria), sourced from 6 locations in their introduced range (39.4 to 48.8° N). The populations were known to have diverged in their critical daylength for diapause since introduction in 1992. After rearing the populations in similar conditions for a generation, and overwintering the adult beetles outdoors, we followed cohorts of eggs on size-matched potted plants as they developed with natural timing through 2 generations in a randomized complete block design. Adult beetles from both the first and second generations were sampled to determine their reproductive status and voltinism. We harvested, dried, and weighed inflorescences and roots of the plants to measure agent impact. The 6 beetle populations were found to differ significantly in both voltinism and impacts, with a higher voltinism corresponding with greater impact. We also showed that voltinism in the introduced location was, to some extent, predictable based on laboratory determined photoperiod response curves, but other factors including plant quality also appeared to be influential. These results show that the efficacy of a biological control agent varies by geographic source and that this can be at least partially predicted by the population's diapause response to photoperiod.

Eastern flower thrips (Frankliniella tritici, Fitch) and soybean thrips (Neohydatothrips variabilis, Beach) are vectors of soybean vein necrosis virus (SVNV) and have increased in importance since the detection of the SVNV in 2008 in Arkansas. Understanding the factors that influence the timing and extent of these insects' activity, along with their predators such as the insidious flower bug (Orius insidiosus, Say), could contribute to improved management. Here, we compiled monitoring data between 2020 and 2023 from the American Midwest Suction Trap Network and examined associations between the timing of early and late activity, cumulative activity density, weather, landscape composition, and host plant phenology. We found that the activity of Eastern flower thrips began earlier, and insidious flower bug activity occurred later when conditions were warmer. In contrast, the activity of soybean thrips began earlier when there was higher edge density in the landscape but was not coincident with the timing of soybean bloom, suggesting an important role for noncrop host plants in early activity of these insects. Despite becoming active later, soybean thrips had greater cumulative activity density where it was warmer, a discordance suggesting the importance of migration in their overall abundance. Suction trap captures might therefore reflect the influences of local conditions as well as migratory movements on soybean thrips activity. Soybean thrips and insidious flower bug cumulative activity densities were also found to be positively correlated, suggesting that insidious flower bugs may be opportunistically utilizing soybean thrips as prey. Continued regional monitoring of these insects could be used to improve vector management.

Little is known about the interaction between different egg parasitoid species parasitizing a single host species, under field conditions. In a 2-yr study, we investigated the efficiency of finding and parasitism of eggs of Dalbulus maidis (DeLong) (Hemiptera: Cicadellidae) by the egg parasitoids Anagrus virlai Triapitsyn (Hymenoptera: Mymaridae) and Paracentrobia subflava (Girault) (Hymenoptera: Trichogrammatidae) in maize fields. Host-finding efficiency was compared in fields of plants that differed in age, and on maize edges versus within the maize fields. Then, host-finding and parasitism during short (1 d) versus long (5 d) exposure periods were compared. Anagrus virlai and P. subflava showed similar, highly efficient host searching of maize leaves baited with D. maidis eggs, with similar efficiency in maize crops of different ages. Host-finding was higher, however, in the maize edges than within the maize field. With regard to speed of finding, whereas both parasitoid species were able to search and parasitize D. maidis eggs (at similar levels) when given 5 d of exposure, only P. subflava was able to find and parasitize D. maidis eggs within 24 h. Host-finding of D. maidis eggs was independent between A. virlai and P. subflava when both species parasitized on a single maize leaf. These results suggest that co-occurrence of both parasitoid species is facilitated because each species finds host eggs at different times, parasitoids adults emerge at different times, and a high quantity of host eggs is available.

Pepper weevil, Anthonomus eugenii Cano, is a devastating pest of pepper that is typically controlled, to varying degrees, with chemical insecticides. Additional tools are needed to manage this pest, including host plant resistance. Field and laboratory studies were conducted over 4 yr to determine pepper weevil preferences for pepper hosts with different Scoville heat units (SHU): bell (0 SHU), jalapeño (2,500 to 8,000 SHU), habanero (100,000 to 350,000 SHU), ghost (855,000 to 1,041,427 SHU), and scorpion (1,200,000 to 2,000,000 SHU) peppers. In field trials, jalapeño had the highest number of weevil-infested fruit, and ghost pepper had the lowest. The number of adult weevils on the foliage was highest in jalapeño (0.94 ± 0.23) and lowest in ghost pepper (0.11 ± 0.05). The density of the weevils inside infested fruit was highest on jalapeño and lowest in scorpion pepper. Laboratory olfactometer tests documented a higher preference of adult weevils for bell and jalapeño followed by habanero, ghost, and scorpion peppers. Differences in plant height and width among hosts were not correlated with weevil infestation level. Pepper weevil host preference appears inversely related to pepper hotness (SHU), as bell and jalapeño peppers, the hosts with the lowest SHUs, were the most susceptible to weevil infestation. The greater weevil susceptibility of jalapeño and bell pepper than other species/cultivars may be related to the fact that jalapeño and bell pepper and the weevil co-evolved in Mexico. This study could help in the selection of resistant pepper species for managing pepper weevil.

Plants emit hundreds, if not thousands, of different volatile chemical compounds, although the function of most individual volatiles remains elusive. Individual volatiles, as well as blends of many chemicals, are likely multifunctional in regulating plant interactions with different groups of insects, including herbivores, natural enemies, and pollinators. However, research on these insect groups has historically been siloed, limiting our understanding of connections between different volatile-mediated ecological processes and how to apply this knowledge to agroecosystems. Here, we review recent literature on volatile multifunctionality in mediating plant interactions with insect herbivores, natural enemies, and pollinators. Ultimately, we propose that future research shifts towards a holistic approach in the study of volatile-mediated interactions between plants and insect communities. By elucidating how specific volatiles, chemical classes, and blends regulate behaviors across different groups of insects, we will uncover new semiochemical tools for controlling pests and protecting beneficial insects in agroecosystems.

Heat waves, brief periods of unusually high temperatures, are increasing in frequency and intensity globally. Such extreme weather events can alter plant chemistry, disrupting species interactions that contribute to pest suppression or increase their performance. Yet, most heat wave studies focus on pairwise interactions, leaving us with a poor understanding of how complex agroecosystems respond to temperature extremes. We addressed this knowledge gap by simulating an experimental heat wave in the field on potato plants (Solanum tuberosum L.) and the Colorado potato beetle, Leptinotarsa decemlineata (Say) (Coleoptera: Chrysomelidae), in the presence or absence of their mutualistic microbial symbionts and another pest, the potato aphid (Macrosiphum euphorbiae (Thomas)). We assessed beetle performance alongside changes in volatile organic compounds (VOCs) and glycoalkaloids from host plants. Beetle performance declined in the absence of their microbial symbionts and under aphid competition, but this effect was reversed under heat wave conditions. These results corresponded with a downregulation in glycoalkaloids, suggesting that potato prioritizes heat stress response over herbivore attack by divesting resources from the production of defensive compounds. The heat wave strongly affected VOCs composition, reducing emissions of multiple compounds while increasing others, but these changes were not directly linked with CPB performance. Overall, our results demonstrate that heat wave effects on crop-pest dynamics are dependent on the agroecological context and mediated by specialized metabolites. Importantly, under dual herbivore pressure, potato crops appear to prioritize coping with heat over defending against pests, underscoring the urgent need for pest management strategies that account for extreme climate events.

When species compete over similar resources, niche partitioning can permit ecologically similar species to coexist. Such coexistence should be a particular challenge for carrion-feeding invertebrates, with the ephemeral nature of carrion leading to intense competition over this nutrient-rich resource. Here we tested whether the carrion niche in four species of coexisting burying beetles (Nicrophorus spp.) is partitioned seasonally or by species size in seven ancient woodlands in the United Kingdom. We fail to replicate the results of previous studies in the UK that found a strict seasonal separation in the activity of competing burying beetle species. Instead, our data support the hypothesis that the niche is partitioned by species size. We present field evidence consistent with the hypothesis that smaller species are less successful at contested carcasses and confirm that sexual dimorphism in head width, a trait likely related to competitive ability, is present in several species of Nicrophorus. We discuss the considerable but as-of-yet unnoticed variation between different geographic populations of Nicrophorus spp. in how the carrion niche is partitioned.