The mechanisms used to facilitate mate location among insects—such as pheromones—can inhibit interspecific attraction and confer reproductive isolation. However, pheromone components seem conserved within the genus Monochamus (Coleoptera: Cerambycidae) with the compound 2-(undecyloxy)ethanol (referred to as monochamol) being identified as the sex-aggregation pheromone or putative pheromone attractant for at least 15 species in this genus. This pheromone parsimony suggests the existence of additional isolating mechanisms. Here we describe the results of laboratory and field assays of additional mechanisms, including laboratory volatile collections and field trapping experiments that assessed the potential presence of additional pheromone components, diel rhythms of pheromone production, and phenological/diel flight activity in the reproductive isolation of sympatric populations of three species of Monochamus in the Great Lakes Forest Region of Ontario, Canada. Chemical analyses of volatile extractions indicate that monochamol is produced by male Monochamus maculosus and Monochamus scutellatus, but no qualitative differences were observed in male extracts of these two species suggesting that there are no additional pheromone components that confer specificity. No quantitative differences were found in the production of monochamol by male M. scutellatus during the photophase and scotophase suggesting there is no diel rhythm in pheromone production. Our results indicate that M. scutellatus flies earlier in the season and day than M. maculosus and Monochamus notatus, which could partially contribute to their reproductive isolation. Overall, no obvious differences in pheromone composition were observed but minor differences in flight times were observed, suggesting other isolating mechanisms may exist.

Graphical Abstract

Herbivorous insects utilize olfactory and visual cues to orient on suitable host plants, and such cues can be employed to facilitate insect monitoring. Lygus lineolaris Palisot de Beauvois is a polyphagous pest throughout North America. Monitoring this pest as it moves between crop and non-crop hosts remains challenging, and a lack of effective monitoring tools complicates management of this insect. In this study, we examined the electrophysiological and behavioral responses of L. lineolaris to the volatile emissions of 2 crop hosts: alfalfa and strawberry. Gas chromatography with electroantennographic detection was applied to identify antennally active compounds in headspace extracts of flowering host plants, before responses to individual compounds were examined in the field. Five compounds consistently elicited antennal depolarizations in adults of L. lineolaris and, of these, (±)-linalool increased the capture rate of L. lineolaris females in the field. Subsequent experiments examined the influence of visual cues and stereochemistry on capture rate, revealing that lures containing (±)-linalool and (S)-(+)-linalool significantly increased the capture rate of L. lineolaris females compared with traps baited with (R)-(-)-linalool and controls, indicating that L. lineolaris is attracted to (S)(+)-linalool. While lures increased capture on red traps, this was not the case for white traps, emphasizing the importance of visual cues in the movements and monitoring of L. lineolaris. This study demonstrates that L. lineolaris is attracted to (S)-(+)-linalool in the field, and that attraction depends on trap color.This knowledge is expected to improve monitoring strategies for L. lineolaris in agricultural systems.

The eastern larch beetle, Dendroctonus simplex LeConte, is a North American species of bark beetle that shares the distribution of its host, Larix laricina (Du Roi) K. Koch. A recent outbreak in the Great Lakes region has prompted renewed interest in the chemical ecology of eastern larch beetle and its natural enemies. Here, we describe field assays elucidating these insects' flight responses to host resin odors and pheromone components in Minnesota and laboratory olfactometer assays illustrating walking responses by eastern larch beetle to pheromone components produced by female beetles. In field trials, the addition of host monoterpenes Δ-3-carene and α-pinene to seudenol lures increased trap captures of eastern larch beetles. Similarly, α-pinene increased captures of Thanasimus spp. predators in seudenol-baited funnel traps. Frontalin release rates between 0.014–3.3 mg/day did not significantly alter catches of eastern larch beetles with seudenol alone, however, still higher concentrations of frontalin (24 mg/day) decreased catches. In contrast, increasing frontalin release rates increased attraction of Thanasimus spp. to seudenol. In a laboratory olfactometer assay, a combination of frontalin and seudenol released at rates comparable to those of a solitary, mining female arrested walking male eastern larch beetles whereas either compound alone did not. Insights into the eastern larch beetle's chemical ecology will improve understanding of cues in host and mate location that may be exploited for management.

Aggregation-sex pheromones, that attract both sexes, are produced by male cerambycid beetles (Coleoptera: Cerambycidae) of the subfamilies Cerambycinae, Lamiinae, and Spondylidinae. Here, we present the results of a field experiment conducted at multiple sites in southern Texas, primarily near the border with the state of Tamaulipas, Mexico. At each site, we deployed traps baited with a 6-component blend of known pheromones of cerambycine and lamiine species + an ethanol lure, a 5-component blend of lamiine pheromones + an ethanol lure, an ethanol lure alone, and a solvent control. Over a ∼3-wk period, 846 beetles of 51 species were trapped, representing 36 cerambycine, 14 lamiine, and one prionine species, and one species in the closely related family Disteniidae. For species collected from at least 5 study sites, nonparametric tests of treatment effects revealed that the generic 6-component blend + ethanol attracted significant numbers of one cerambycine species, while the lamiine blend + ethanol attracted one cerambycine species and 2 lamiine species. The ethanol lure attracted 2 additional cerambycine species in significant numbers. For species that were captured at fewer sites, chi-square goodness-of-fit tests showed that the 2 pheromone blends + ethanol attracted significant numbers of another 6 species of cerambycines and 4 species of lamiines. Captures noteworthy from the standpoint of collection records include the rare species Leptostylopsis lutea Dillon, and Lochmaeocles cornuticeps cornuticeps (Schaeffer) and Thryallis undatus (Chevrolet), 2 species which have rarely been reported outside Sabal Palm Sanctuary in Cameron County, Texas.

Disturbance plays a critical role in the ecology of forests including influencing the abundance and diversity of fauna. Although numerous studies have focused on forest responses to various disturbance events, less attention has been given to arthropod community responses. California experienced an extreme, multi-year drought from 2012 to 2015 which severely stressed trees and incited epidemics of several bark beetle species (Coleoptera: Curculionidae: Scolytinae). Water stress and bark beetles contributed to a significant mortality event of hundreds of millions of trees in the central and southern Sierra Nevada, causing significant structural and compositional changes in forests. Our study sought to characterize woodborer and wood-decay-related beetle responses to various levels of tree mortality and snag (dead standing tree) retention resulting from this tree mortality event. Of particular interest were responses to differences in the orientation of dead wood, standing snags versus fallen snags. Ethanol-baited panel flight intercept traps were deployed for multiple weeks in 2022 and 2023 on plots representative of 3 disturbance classes: (i) low tree mortality (<30%), (ii) high tree mortality (>50%) with low snag fall (≤50%), and (iii) high tree mortality (>50%) with high snag fall (>60%). Woodborers and wood-decay-related beetle assemblages were compared at the family and species level. Our analyses revealed several significant differences in community assemblages among disturbance classes. Despite these differences, our results failed to reveal clear, qualitatively distinctive assemblages among disturbance classes. Rather, we could only conclude general patterns from the observed dissimilarities in richness and abundance. In general, we observed a greater diversity of woodborers on high-mortality plots than on low-mortality plots. Similarly, the diversity of wood-decay-related beetles generally increased with greater amounts (basal area) of snag fall.The amount of tree mortality and snag fall were positively related to several woodborer and wood-decay-related beetles. Observed beetle assemblages, their corresponding life histories, and the influences of altered habitat availability are discussed.

Exotic granulate ambrosia beetle, Xylosandrus crassiusculus (Motschulsky), black stem borer, Xylosandrus germanus (Blandford), and black twig borer, Xylosandrus compactus (Eichhoff) are serious pests of woody ornamental trees in nurseries. Woodlots often surround ornamental nurseries, where the ambrosia beetles fly into nurseries and attack young trees.The woodlots are either dominated by hardwood trees, such as Oaks (Oak spp.), maples (Acer spp.), or pine trees, mainly loblolly pine (Pinus taeda L.). It is unclear if the woodlot type would influence the abundance of ambrosia beetle pests flying outside the woodlot.Thus, this study aimed to determine whether the hardwood or pine-dominated stand affects the relative abundance of ambrosia beetle pests outside the woodlot. In 2023 and 2024, experiments were conducted by deploying 3 ethanol-lured plastic bottle traps in 4 hardwood and 4 pine-dominated woodlots in mid-Georgia (USA). The overall captures of X. crassiusculus and X. germanus were significantly greater in the hardwood than in the pine-dominated woodlots in both years.The numbers of X. crassiusculus and X. germanus collected in traps were not consistently significantly different between the hardwood and pine-dominated woodlots for most sampling dates.The captures of X. compactus were not influenced by woodlot type. This suggests that although ambrosia beetle pests were collected from both hardwood and pine-dominated woodlots in both years, the risk of infestation in nurseries is greater from the adjacent hardwood than pine-dominated woodlots.

Stored-product insects may pose food safety concerns due to their capacity to vector harmful microbes. As climate change progresses, the propensity for vectoring may be affected by temperature. Vectoring capacity may also fluctuate over the season. Thus, we evaluated (i) how the area of microbial growth and morphospecies richness vary over the season from field-collected Sitophilus oryzae that were allowed to disperse onto a novel food patch habitat comprised of agar and (ii) whether temperature in the week preceding collection of S. oryzae affected growth and richness. On a weekly basis during 2022 and 2023, we introduced S. oryzae onto agar, and photographed patches at 3 and 5 d, characterizing growth with ImageJ and visually scoring richness.There was 1.4- to 1.6-fold more microbial growth in patches at 5 d compared to 3 d in both years. The greatest microbial growth consistently occurred from S. oryzae collected during the wheat and maize harvest in grain bins, while morphospecies richness increased progressively over time. We observed an 11-fold and 3-fold increase in the number of morphospecies at the end of the season compared to the beginning in 2022 and 2023. There was 2.1- to 316-fold more microbial growth during the wheat (Jun to Jul) and maize harvest (Sep to Oct) compared to early May. We found a positive exponential relationship between temperature in the field and microbial growth in both years. This study expands our understanding of insect–microbe interactions after harvest and highlights variable periods of risk by food facilities over the season.

Graphical Abstract

Pesticides released into the environment are increasingly recognized as a global threat to freshwater ecosystems because of their adverse effects on non-target organisms, particularly aquatic insects and other arthropods. Superoxide dismutases (SODs) are important antioxidant enzymes that play a crucial role in protecting organisms from oxidative stress induced by harmful materials. In this study, we identified 2 cellular SODs (PxSOD1 and PxSOD2) in Protohermes xanthodes Navás (Megaloptera: Corydalidae), an freshwater predatory insect, and determined the oxidative stress induced in P. xanthodes larvae by sublethal exposure to chlorpyrifos (CPF). PxSOD1 and PxSOD2 are members of the cytoplasmic Cu/ZnSODs and mitochondrial MnSODs, respectively, and differ substantially in protein structure. Both PxSOD1 and PxSOD2 recombinant proteins demonstrated catalytic activity toward O₂ ^•– in the activity assays. After exposure to sublethal concentrations of CPF, malondialdehyde (MDA) content and SOD activities were increased in P. xanthodes larvae in a dose-dependent manner. PxSOD1 expression was decreased in the 0.42 and 4.2 µg/L CPF groups and increased in the 4.2 µg/L CPF group. PxSOD2 was upregulated by 0.42, 4.2, and 8.4 µg/L CPF treatments and the expression levels in the 4.2 and 8.4 µg/L CPF groups were significantly higher than that in the no CPF control. Our results suggest that sublethal concentrations of CPF can induce oxidative stress in P. xanthodes larvae, and the cellular SODs in P. xanthodes larvae may contribute to the protection against CPF-induced oxidative stress.

Graphical Abstract

The stimulatory and protective response known as hormesis elicits an often over compensatory response resulting in life-history trait improvements.There are an array of abiotic and biotic agents that have been shown to trigger hormesis; most commonly studied are chemicals, temperature, and low oxygen. Investigations into low-oxygen exposures that activate the hormetic response reveal that insect performance can be dramatically improved by single short low-oxygen events, but the focus of this work has been primarily on short-term, transitory protection afforded by hormesis. Few reports examine whether the effect is longer lasting or lifelong. We previously reported that one hour of anoxia was enough to induce a hormetic response in the alfalfa leafcutting bee, Megachile rotundata (Hymenoptera: Megachilidae). Here, we investigated the long-term effects of this response by looking at starvation resistance, flight, and locomotory activity throughout the life of the adult bees. In addition, we studied the effects of anoxia hormesis on multiple reproductive metrics. Anoxia hormesis had lifelong positive effects for flight in both sexes. We also recorded higher starvation survival in bees that experienced hormesis.This improvement in performance came at a steep reproductive cost (ie reduction in fecundity). However, no costs or benefits were passed to the next generation. We hypothesize that using anoxia hormesis in the context of pollination services by this species should result in bees that are more active in the field, thereby increasing the numbers of visits to flowers throughout their entire life.

The larval stage of the army cutworm, Euxoa auxiliaris (Grote), is an agricultural pest in the Great Plains region of North America. Adult migration to alpine aggregation sites to escape extreme summer temperatures and depleted food resources provides a critical food resource for the grizzly bear, Ursus arctos horribilis (Linnaeus, Carnivora: Ursidae), in the Rocky Mountains. However, little is understood about the ecological consequences of the thermal tolerance of adult E. auxiliaris. Therefore, we investigated thermal tolerance of lab-reared and wild-caught individuals by assessing their critical thermal limits (CTL_max and CTL_min). Using a ramping tolerance assay, we began at 25 °C and adjusted the temperature at a rate of 0.3 °C/min until individuals lost control of their righting response. Adult moths had a CTL_max (lab-reared: 44.13 °C, wild-caught moths: 43.28 °C) typical for a temperate lepidopteran species. However, their CTL_min (lab-reared: –2.24 °C, wild-caught: –1.9 °C) reflects an extraordinary ability to remain active and feed when ambient temperatures are low. These findings provide insights into the thermal ecology of E. auxiliaris which are essential for predicting the range distribution of the species, and, consequently, the continued availability of this key food source for Rocky Mountain grizzly bears. As climate change continues to affect ambient temperatures, these results underscore the importance of studying thermal tolerance to anticipate ecological shifts and ensure the conservation of both E. auxiliaris and the grizzly bears that depend on them.

Colonizing aphids play an important role in the transmission of RNA phytoviruses in the family Solemoviridae. According to “host manipulation hypothesis,” phloem limited and persistently transmitted Solemoviridae viruses modulate host physiology that positively affects vector behavior and fitness and facilitates virus spread. However, it is unclear if virus-modulated host effects on vectors across pathosystems involving Solemoviridae members are always positive. Cotton leafroll dwarf virus (CLRDV) is a recently introduced Solemoviridae member in the United States, and it is transmitted by the cotton aphid (Aphis gossypii). Effects of CLRDV infection on vector behavior and fitness were evaluated on its primary host plant, cotton (Gossypium hirsutum), and an alternate host plant, hibiscus (Hibiscus acetosella). In this study, changes to viruliferous and non-viruliferous aphid preference and aphid fitness on virus-infected and non-infected hosts were examined. In contrast to the hypothesized preference of non-viruliferous aphids for infected plants and vice-versa, both viruliferous and non-viruliferous A. gossypii preferred non-infected cotton and hibiscus plants over CLRDV-infected plants.This suggested that the preference of non-viruliferous vectors to non-infected plants might negatively impact virus acquisition, whereas the preference of viruliferous vectors toward non-infected plants could positively facilitate virus inoculation. The total fecundity and intrinsic rate of increase of aphids were higher on non-infected plants compared with CLRDV-infected plants. The lack of enhanced fitness benefits on CLRDV-infected hosts also could negatively impact virus spread. Overall, this study suggested that “host manipulation hypothesis” favoring vector attraction and enhanced fitness on infected plants does not apply to all pathosystems involving Solemoviridae members.

Nectar is an important source of food for adult mosquitoes, influencing their biological characteristics including longevity, fecundity, and flight range. Consequently, it can impact mosquitoes' survival and efficiency in transmitting disease. Different mosquito species are known to show preferences for flower nectar from certain plants, yet despite the importance of these plant–mosquito associations, knowledge of such biotic interactions is sparse. Here, we present a systematic map to address the question: “Which nectar do mosquitoes feed on?.” The mapping process identified 49 articles (comprising 51 studies) meeting inclusion criteria, detailing 397 records of 74 mosquito species feeding on nectar from 145 plant species and 109 genera. Data extracted from the map were then analyzed to better understand if mosquitoes showed preferences for specific plant nectar. A key finding from this study is clear evidence supporting the hypothesis that mosquitoes exhibit preferences for nectar from particular plant species, including 77 species of plants and 58 genera for Aedes species, 18 species of plants and 17 genera for Anopheles species, and 16 species of plants and 16 genera for Culex species (all 3 genera belong in Diptera: Culicidae). Our study also highlighted the need for further field and laboratory work in time and space and using methods that randomly selects plant species for investigation. This would facilitate a better understanding of the relationship between mosquito feeding behavior and nectar seasonality and abundance; data that are critical for the development and improvement of new mosquito control methods to tackle vector-borne diseases.

A new population of the Asian longhorned beetle (Anoplophora glabripennis Motschulsky), an invasive species in North America since 1996, was discovered in Charleston County, South Carolina, in 2020. This population is the furthest south Asian longhorned beetle has established in North America. Previous models only estimate development time at this latitude; as such, we examined Asian longhorned beetle phenology in this novel climate. Over 24 consecutive months, we collected 153 eggs, 878 larvae, 37 pupae, and 1 unemerged adult (1,009 total specimens) from the federal quarantine zone in South Carolina and used larval head capsule width to determine development rate and voltinism. The presence of Asian longhorned beetle adults was determined via visual field observations. Asian longhorned beetle in South Carolina appears to have a synchronous univoltine life cycle, in contrast to populations in the northern United States and Canada that typically develop in 2–3 yr. This information will be useful for future model development to determine Asian longhorned beetle life cycles, for implementing novel management methods, and will aid in predictions to benefit visual survey efficacy.

Corn earworm, Helicoverpa zea Boddie (Lepidoptera: Noctuidae), is a common herbivore that causes economic damage to agronomic and specialty crops across North America.The interannual abundance of H. zea is closely linked to climactic variables that influence overwintering survival, as well as within-season host plant availability that drives generational population increases. Although the abiotic and biotic drivers of H. zea populations have been well documented, prior temporal H. zea modeling studies have largely focused on mechanistic/simulation approaches, long term distribution characterization, or degree day-based phenology within the growing season. While these modeling approaches provide insight into H. zea population ecology, growers remain interested in approaches that forecast the interannual magnitude of moth flights which is a key knowledge gap limiting early warning before crops are planted. Our study used trap data from 48 site-by-year combinations distributed across North Carolina between 2008 and 2021 to forecast H. zea abundance in advance of the growing season.To do this, meteorological data from weather stations were combined with crop and soil data to create predictor variables for a random forest H. zea forecasting model. Overall model performance was strong (R² = 0.92, RMSE = 350) and demonstrates a first step toward development of contemporary model-based forecasting tools that enable proactive approaches in support of integrated pest management plans. Similar methods could be applied at a larger spatial extent by leveraging national gridded climate and crop data paired with trap counts to expand forecasting models throughout the H. zea overwintering range.

The non-native wood-boring and symbiotic fungus-culturing Xylosandrus germanus (Blandford) was first reported in New York apple orchards in 2013. Trapping surveys have been conducted annually since to assist growers in timely applications of preventative control measures. In 2021, a similar-looking introduced species, Anisandrus maiche (Kurentsov), was identified in traps in west central New York. Anisandrus maiche was first recorded in 2005 in Pennsylvania but its history in New York was unclear due to potential misidentification. We collected and identified ambrosia beetles using ethanol-baited bottle traps in 2022 and 2023 in New York at 2 commercial apple orchards near Lake Ontario and 2 cider apple orchards in the lower Finger Lakes district. Traps were placed in a forest interior, the forest edge, and the orchard edge at each site. Xylosandrus germanus was trapped from mid-April into early October; it was abundant in the Lake Ontario region but less so in the Finger Lakes. In contrast, counts of A. maiche were very high in the Finger Lakes but extremely low near Lake Ontario. It was trapped from late-May to mid-September. Most other bark and ambrosia beetle species were uncommon. Captures of X. germanus and A. maiche were generally highest in the forest interior and declined toward the orchard edge, but each species was usually present in traps across habitats at the same time. Thus, the practice of trapping at forest edges should continue. Both species can potentially infest stressed trees, including in orchards, throughout the growing season.

Understanding and optimizing rearing conditions for dragonfly larvae is crucial for ecological research and conservation efforts, yet optimal rearing conditions and general rearing practices are lacking. In this study, we investigated the effect of temperature, amount of oxygen in water, presence of (artificial) plants, and age of eggs on hatchability, survival, and development of dragonfly larvae using the model species Sympetrum striolatum. We conducted three independent experiments and assessed variability between egg clutches of individual females, as well as the occurrence of cannibalism among larvae. Our results showed that egg hatchability varied significantly between individual females and was negatively affected by egg aging and the presence of artificial plants. Larval survival was negatively affected by water temperatures above 24°C, the presence of artificial plants, and egg aging, and positively affected by high feeding frequency, in certain instars. Notably, cannibalism was observed among later instar larvae, especially under higher density conditions. Based on these findings, we provide practical recommendations for optimizing dragonfly larvae rearing protocols, emphasizing the importance of maintaining optimal temperature, appropriate feeding regimes, and managing larval density to reduce cannibalism. This study offers experimental, evidence-based guidelines for dragonfly larvae rearing, contributing to improved research methodologies and conservation efforts.