Large Beetle Research Articles

Diet of raccoon dogs (Nyctereutes procyonoides) in Danish wetlands with focus on ground-nesting birds and amphibians

In European countries, raccoon dogs (Nyctereutes procyonoides) are believed to impact ecosystems and potentially threaten native species. In this study, the stomachs of 525 raccoon dogs culled in Danish wetlands were analysed and compared to 53 stomachs of adult raccoon dogs killed by vehicles, from the countryside. The stomach content was analysed using traditional macroscopic technics supplemented by eDNA analysis. The diet of raccoon dogs in wetlands did not differ notably from that of raccoon dogs in other parts of Denmark except for the larger amount of bait, and less shrews and fruit. More than 80% of the diet of adult raccoon dogs in wetlands consisted of bait, birds (mainly ducks taken in autumn and songbirds), amphibians, carrion, berries, fruit, and grass. Also, insects (mainly larger beetles and aquatic insects) occurred in the diet of raccoon dogs in wetlands. Waterfowl eaten during the autumn and winter are likely to be migrating birds. A high number of carrion beetles and fly maggots indicates a high consumption of carrion of all kinds. Eggs of ground-nesting birds made up a negligible part of the raccoon dog’s diet. eDNA-analysis found no trace of shorebirds and only common species of amphibians were recorded. This study provides no evidence that raccoon dogs are a threat to ground-nesting birds nor to endangered amphibians in Danish wetlands.

The Australian Museum and Friends of Lord Howe survey of large Coleoptera on Lord Howe Island, August 2022

A survey of large beetles, one centimetre or more in length, on Lord Howe Island, was conducted in August 2022 and the results are discussed. In total, 32 large species were found. This was the first survey made at least one beetle generation after eradication of the rodents in 2019, and there was some evidence of recovery, in particular of the large flightless endemic cerambycid, Xylotoles wollastoni (White, 1856), but also of a leaf beetle, Dematochroma picea (Baly, 1864) and an exotic pest of lawns, Heteronychus arator (Fabricius, 1775). There was also evidence of recovery of Carabidae species after the prolonged dry years of 2016 to 2019.

Tracheal hyperallometry and spatial constraints in a large beetle

Insects exchange respiratory gases with their environment through their gas-filled tracheal system, a branched tracheal tree extending from segmental openings and terminating at fine tissue penetrating tracheoles. It was shown that the tracheal volume increases hyperallometrically with insect body size (Mb), both interspecifically and across developmental stages. In this study, we used the sixfold Mb variation in adult Batocera rufomaculata(Cerambicidae; Coleoptera) examining the allometry of adult tracheal volume (Vtr). We further explored the effect of sex and sexual maturity on tracheal gas conductance, testing the hypotheses that (i) larger body size and (ii) egg volume in gravid females would result in lower safety margins for tracheal oxygen transport due to structural restriction. We report a hyperallometric tracheal growth in both sexes of adult B. rufomaculata(mean mass exponent of 1.42 ± 0.09), similar in magnitude to previously reported values. Tracheal gas conductance was independent of Mb and reproductive state, but was significantly higher in females compared with males. We suggest that females may have pre-adapted a higher tracheal conductance required for the higher flight power output while gravid. Lack of compliant air sacs and rigid trachea may explain how gravid females retain their Vtr. However, we show that Vtr outgrows thoracic dimensions with increased B. rufomaculatasize. Hyperallometric growth of the giant cerambycid thoracic trachea could explain the previously reported hypometric scaling of flight muscles in B. rufomaculata, and the compromised long-distance flight performance of larger compared with smaller conspecifics.

Drone microrelief analysis to predict the presence of naturally regenerated seedlings

Three-dimensional (3D) mapping and unmanned aerial vehicles (UAVs) are essential components of the future development of forestry technology. Regeneration of forest stands must be ensured according to the law in the required quality and species composition. Forest management focuses on the optimization of economic costs and quality-assured seedlings. Predicting the suitability of the plots’ environment for natural forest regeneration can contribute to better strategic planning and save time and money by reducing manual work. Although the savings may be considered negligible on small forested plots, they are significant for large cleared areas, such as those harvested after large beetle infestations or strong windstorms, which are increasingly common in European forests. We present a methodology based on spatial analysis and 3D mapping to study the microrelief and surrounding of recently cleared areas. We collected data on four plots in the spring and autumn of a single year after the harvest of four Norway spruce [Picea abies (L.) Karst.] stands near Radlice, Czechia using a multirotor Phantom 4 Pro UAV with a red, green, blue (RGB) camera. We used RGB imagery to compute microrelief data at a very high spatial resolution and the surrounding forest stands after harvesting. We used the microrelief data to estimate the amount of water accumulation and incoming solar radiation across the sites. Based on presence data of newly-established seedlings, we used linear mixed effects models to create a suitability map for each site. Model variables included topographic wetness index, solar area radiation, fencing, type of soil preparation, and distance to the nearest mature forest edge. The topographic wetness index and fencing had strong positive influence on seedling establishment, while solar radiation had a negative influence. Our proposed methodology could be used to predict spontaneous regeneration on cleared harvest areas, or it can estimate how much area is suitable for regeneration, which can lead to important investment decisions.

Methionol as an aggregation-sex pheromone of the desert-dwelling beetle Eustromula valida (Coleoptera: Cerambycidae).

As part of a long-term project on unraveling the use of pheromones in the large beetle family Cerambycidae, field trials were conducted with generic blends of known cerambycid pheromones at a desert site in southern California. In the first year of testing (2022), the species Eustromula valida (LeConte) (subfamily Cerambycinae, tribe Elaphidiini) and Aethecerinus latecinctus (Horn) (Cerambycinae, Trachyderini) were weakly attracted to one of the lure blends. In follow-up trials in 2023, only E. valida were caught, and collection of volatiles from both sexes of E. valida determined that males sex-specifically produced 3-methylthiopropan-1-ol (methionol), a compound that was not in the tested lure blends. Beetles of both sexes were strongly and specifically attracted to this compound in field bioassays, verifying that it is an aggregation-sex pheromone. No sympatric species were attracted to methionol while it was deployed in the field. Several recent studies have identified methionol as a pheromone component for other cerambycid species in both North and South America, suggesting it may represent another common pheromone component within the Cerambycidae.

Dataset: Biodiversity of Ground Beetles (Coleoptera, Carabidae) of the Republic of Mordovia (Russia)

(1) Background: Carabidae is one of the most diverse families of Coleoptera. Many species of Carabidae are sensitive to anthropogenic impacts and are indicators of their environmental state. Some species of large beetles are on the verge of extinction. The aim of this research is to describe the Carabidae fauna of the Republic of Mordovia (central part of European Russia); (2) Methods: The research was carried out in April-September 1979, 1987, 2000, 2001, 2005, 2007–2022. Collections were performed using a variety of methods (light trapping, soil traps, window traps, etc.). For each observation, the coordinates of the sampling location, abundance, and dates were recorded; (3) Results: The dataset contains data on 251 species of Carabidae from 12 subfamilies and 4576 occurrences. A total of 66,378 specimens of Carabidae were studied. Another 29 species are additionally known from other publications. Also, twenty-two species were excluded from the fauna of the region, as they were determined earlier by mistake (4). Conclusions: The biodiversity of Carabidae in the Republic of Mordovia included 280 species from 12 subfamilies. Four species (Agonum scitulum, Lebia scapularis, Bembidion humerale, and Bembidion tenellum) were identified for the first time in the Republic of Mordovia.

Intraspecific scaling and early life history determine the cost of free-flight in a large beetle (Batocera rufomaculata).

The scaling of the energetic cost of locomotion with body mass is well documented at the interspecific level. However, methodological restrictions limit our understanding of the scaling of flight metabolic rate (MR) in free-flying insects. This is particularly true at the intraspecific level, where variation in body mass and flight energetics may have direct consequences for the fitness of an individual. We applied a 13C stable isotope method to investigate the scaling of MR with body mass during free-flight in the beetle Batocera rufomaculata. This species exhibits large intraspecific variation in adult body mass as a consequence of the environmental conditions during larval growth. We show that the flight-MR scales with body mass to the power of 0.57, with smaller conspecifics possessing up to 2.3 fold higher mass-specific flight MR than larger ones. Whereas the scaling exponent of free-flight MR was found to be like that determined for tethered-flight, the energy expenditure during free-flight was more than 2.7 fold higher than for tethered-flight. The metabolic cost of flight should therefore be studied under free-flight conditions, a requirement now enabled by the 13C technique described herein for insect flight.

Disentangling thermal from alternative drivers of reflectance in jewel beetles: A macroecological study

AbstractAimTo predict future colour–climate relationships, it is important to distinguish thermal drivers of reflectance from other evolutionary drivers. We aimed to achieve this by comparing relationships between climate and coloration in ultraviolet–visible (UV–Vis) and near‐infrared (NIR) light, separately.LocationSamples were distributed primarily across Australia and North America, with some from Africa and Asia.Major taxa studiedColeoptera: Buprestidae.MethodsWe used jewel beetles as models to identify climatic drivers of reflectance, because jewel beetles have highly diverse coloration and a wide distribution and are often active in hot conditions. Specifically, we tested the association between climate, body size and reflectance using a phylogenetic comparative analysis for three wavebands (UV–Vis, NIR and total).ResultsReflectance of jewel beetles was more strongly predicted by body size than by climate. NIR reflectance and total reflectance were not associated with climate, but larger beetles had higher NIR reflectance. For UV–Vis reflectance, small beetles were darker in warmer and more humid environments, whereas there was no association with climate for large beetles.Main conclusionsOur study suggests that variation in reflectance of jewel beetles is not driven by thermal requirements and highlights the importance of considering NIR reflectance when evaluating explanations of the effects of colour on thermoregulation.

A test of the competitive ability–cold tolerance trade‐off hypothesis in seasonally breeding beetles

Abstract Closely related species that use similar resources often differ in their seasonal patterns of activity, but the factors that limit their distributions across seasons are unknown for most species. One hypothesis to explain seasonal variation in the distributions of species involves a trade‐off between competitive ability and cold tolerance, where tolerance to the cold compromises competitive ability in warmer (benign) temperatures, either at the level of the individual or population. We tested both individual‐level and population‐level mechanisms of this hypothesis in two co‐occurring species of temperate burying beetles (Silphidae: Nicrophorus sayi, N. orbicollis) that differ in their seasonal patterns of activity. We measured cold tolerance, breeding activity as a function of temperature, and competitive ability as a function of temperature and season. Consistent with our hypothesis, the mid‐season N. orbicollis was less able to function at the cold temperatures that characterise early spring, when the early‐season N. sayi is most active. The larger beetle, however, always won one‐on‐one competitive trials at warm temperatures, regardless of species, inconsistent with an individual‐level trade‐off. N. orbicollis was usually larger and successful when competing for the same carrion later in the season, mostly because of its larger population size, consistent with a trade‐off between competitive ability, and cold tolerance acting at the population level. Our findings suggest that cold temperatures limit the mid‐season N. orbicollis from earlier spring emergence, while competitive pressure from the more abundant, larger N. orbicollis constrains the early‐season N. sayi from remaining active through the summer.

Isometric spiracular scaling in scarab beetles-implications for diffusive and advective oxygen transport.

The scaling of respiratory structures has been hypothesized to be a major driving factor in the evolution of many aspects of animal physiology. Here, we provide the first assessment of the scaling of the spiracles in insects using 10 scarab beetle species differing 180× in mass, including some of the most massive extant insect species. Using X-ray microtomography, we measured the cross-sectional area and depth of all eight spiracles, enabling the calculation of their diffusive and advective capacities. Each of these metrics scaled with geometric isometry. Because diffusive capacities scale with lower slopes than metabolic rates, the largest beetles measured require 10-fold higher PO2 gradients across the spiracles to sustain metabolism by diffusion compared to the smallest species. Large beetles can exchange sufficient oxygen for resting metabolism by diffusion across the spiracles, but not during flight. In contrast, spiracular advective capacities scale similarly or more steeply than metabolic rates, so spiracular advective capacities should match or exceed respiratory demands in the largest beetles. These data illustrate a general principle of gas exchange: scaling of respiratory transport structures with geometric isometry diminishes the potential for diffusive gas exchange but enhances advective capacities; combining such structural scaling with muscle-driven ventilation allows larger animals to achieve high metabolic rates when active.

Characteristics of the great bustard (Otis tarda) (Otididae, Aves) habitats in the Trans-Volga region according to food availability during the chick rearing period

The results of our studies of potential nesting sites for bustards in the Saratov Trans-Volga region are presented. Characteristics of plant communities, as well as the quantitative and qualitative composition of arthropods in these areas, are given. Specific materials obtained in 2017–2021 at 6 plots are given, namely: crops of winter wheat, millet, and sunflower; fallows of various ages; and young (2nd stage) and old virgin lands. The obtained results are compared with the data of previous years. The obtained results on the state of the forage base of bustards allow us to conclude that loss of nesting habitats by birds of this species has actually occurred. Those areas, where, despite the decrease in the abundance of insects, there are still enough of them to feed the chicks, are not used by bustards as nesting stations. These are fallows of various ages and virgin lands. The lack of a sufficient number of arthropods necessary for feeding chicks in those places where bustards prefer to nest, namely, cereals crops, leads to catastrophic consequences for reproduction, and, consequently, the survival of the species. The numbers of large orthoptera and beetles in winter crops, reflecting biomass indicators, have decreased by 10 times compared to 2000, during the period of extensive agriculture. The intensification of agricultural production, the use of pesticides on various crops, as well as the change in the structure of crop rotation are the main causes for the insufficient food supply during the period of rearing chicks. The results obtained give grounds to believe that the number of bustards will continue to decline due to the inability to raise their offspring as a result of the lack of food supply.

Life history patterns of coleopteran pollinators of Annona crassiflora Mart. in the Brazilian Cerrado

ABSTRACT The large floral chambers of the Neotropical Annonaceae are pollinated by large beetles of the tribe Cyclocephalini Laporte (Melolonthidae). Previous research indicates that, depending on the geographic area, the assemblage of Cyclocephalini pollinators may differ. In this study, pollinators of Annona crassiflora Mart. were surveyed in the Cerrado of Chapada dos Guimarães, Mato Grosso, Brazil, for the first time. The analysis of 74 flowers from 24 A. crassiflora individuals revealed that the principal pollinator was Cyclocephala octopunctata Burmeister. The secondary pollinator, Cyclocephala celata Dechambre, and C. octopunctata exhibited behaviour that may promote cross pollination, visiting both female- and male-phase flowers, touching stigmas and anthers and becoming coated in pollen during anthesis. This is the first record of C. celata, a species commonly found pollinating Araceae in the Atlantic Forest, as a pollinator of an Annonaceae species in the Cerrado. Additionally, an interim phase between the female and male phases of A. crassiflora is documented here for the first time.

New Nesting Records and Breeding Ecology Observations of Rufous-Legged Owls in the Mediterranean Temperate Forest of Central Chile

ABSTRACT The Rufous-legged Owl (Strix rufipes) is the southernmost Strix owl species and its breeding ecology remains little known. We report new observations on the species' breeding ecology, including clutch size, egg size, duration of the incubation and nestling periods, and nestling diet. We conducted our observations on nests found during the summers of 1999 through 2004 in a forestry landscape of central Chile, dominated by Monterey pine (Pinus radiata) plantations with intermixed fragments of native southern beech (Nothofagus) forests. Clutch size was two eggs (n = 2 nests), with one egg larger than the other (mean = 48.8 × 40.1 mm). The incubation period was 30 d and the nestling period 34 d. We analyzed 10 pellets from nestling owls and identified 45 prey items, mostly dominated by large beetles, grasshoppers, and rodents (native and exotic). This information, though based on a limited number of nests, provides baseline ecological data that can inform future studies.

Differential Attraction of Large and Small Tunneling Dung Beetles (Coleoptera: Geotrupidae and Scarabaeidae) to Native Mammal Dung in a Satoyama Forest in Central Japan

Differential Attraction of Large and Small Tunneling Dung Beetles (Coleoptera: Geotrupidae and Scarabaeidae) to Native Mammal Dung in a Satoyama Forest in Central Japan

Unequivocal Differences in Predation Pressure on Large Carabid Beetles between Forestry Treatments

Carabid beetles (Coleoptera: Carabidae) are considered as one of the most cardinal invertebrate predatory groups in many ecosystems, including forests. Previous studies revealed that the predation pressure provided by carabids significantly regulates the ecological network of invertebrates. Nevertheless, there is no direct estimation of the predation risk on carabids, which can be an important proxy for the phenomenon called ecological trap. In our study, we aimed to explore the predation pressure on carabids using 3D-printed decoys installed in two types of forestry treatments, preparation cuts and clear cuts, and control plots in a Hungarian oak–hornbeam forest. We estimated the seasonal, diurnal and treatment-specific aspects of the predation pressure on carabids. Our results reveal a significantly higher predation risk on carabids in both forestry treatments than in the control. Moreover, it was also higher in the nighttime than daytime. Contrarily, no effects of season and microhabitat features were found. Based on these clues we assume that habitats modified by forestry practices may act as an ecological trap for carabids. Our findings contribute to a better understanding of how ecological interactions between species may change in a modified forest environment.

Floral Resources Enhance Fecundity, but Not Flight Activity, in a Specialized Aphid Predator, Hippodamia convergens (Coleoptera: Coccinellidae)

Adult aphid predators disperse across the landscape seasonally in search of prey aggregations that are patchily distributed and temporally variable. However, flight is energetically costly and consumes resources that could be invested in reproduction. Hippodamia convergens is an important aphid predator in North American cereal crops and other agricultural systems. Consumption of floral resources can enhance adult survival during periods of low prey availability and may improve reproductive success. We tested how an omnivorous adult diet containing floral resources (diluted honey and pulverized bee pollen) interacts with body size to influence reproduction and flight behavior compared to a prey-only diet. Two sizes of beetles were produced by controlling larval access to food—3 h daily access produced small beetles; ad libitum access produced large beetles with faster development. Reproductive performance was tracked for 18 days, and female flight activity was assayed via 3 h bouts of tethered flight. Diet composition and body size interacted to influence preoviposition period, with large females in prey-only treatments delaying oviposition the longest. The omnivorous adult diet improved 18-day fecundity relative to a prey-only diet, but egg fertility was unaffected. Adult size affected oviposition pattern, with small beetles laying smaller, but more numerous, clutches. Females flew up to 7 km in 6 h, but neither body size nor adult diet influenced flight distance, suggesting that all diet treatments generated energy reserves sufficient to power flights of short duration. However, pre-reproductive females flew > 60% further than they did post-reproduction, likely due to the energetic costs of oviposition. Thus, access to pollen and nectar increased reproductive success and altered oviposition patterns in H. convergens, indicating the importance of floral resources in the agricultural landscape to conservation of this predator and its biological control services.

Concerted evolution of body mass, cell size and metabolic rate among carabid beetles

Alterations in cell number and size are apparently associated with the body mass differences between species and sexes, but we rarely know which of the two mechanisms underlies the observed variance in body mass. We used phylogenetically informed comparisons of males and females of 19 Carabidae beetle species to compare body mass, resting metabolic rate, and cell size in the ommatidia and Malpighian tubules. We found that the larger species or larger sex (males or females, depending on the species) consistently possessed larger cells in the two tissues, indicating organism-wide coordination of cell size changes in different tissues and the contribution of these changes to the origin of evolutionary and sex differences in body mass. The species or sex with larger cells also exhibited lower mass-specific metabolic rates, and the interspecific mass scaling of metabolism was negatively allometric, indicating that large beetles with larger cells spent relatively less energy on maintenance than small beetles. These outcomes also support existing hypotheses about the fitness consequences of cell size changes, postulating that the low surface-to-volume ratio of large cells helps decrease the energetic demand of maintaining ionic gradients across cell membranes. Analyses with and without phylogenetic information yielded similar results, indicating that the observed patterns were not biased by shared ancestry. Overall, we suggest that natural selection does not operate on each trait independently and that the linkages between concerted cell size changes in different tissues, body mass and metabolic rate should thus be viewed as outcomes of correlational selection.

Bioecological peculiarities and economic significance of large fruit bark beetle (Scolytus mali Bechstein, 1805) and fig bark beetle (Hypoborus ficus Erichson, 1836) in the southern slopes of the Great Caucasus (Azerbaijan)

Background. Bark beetles (Coleoptera, Curculionidae, Scolytinae) are major pests of wood-fruit trees, and infestations often accelerate tree death. Bark beetles are insects that are closely related to their host trees. According to the type of feeding they belong to xylophages [7]. They prefer weakened, sick or damaged trees. Thus, bark beeteles can more easily penetrate into trees affected by various natural phenomena (wind, storm, rain) or primary pests. They are hardly ever found in rotting trees. The research was carried out on the southern slopes of the Great Caucasus during the period 2013–2016. The great difference in the altitude in the study area results in a variety of natural conditions. This, in turn, leads to the richess of fauna and flora of the area. Thus, valuable fruit trees grow both in the forests and fruit farms of the study region. However, large numbers of fruit trees are attacked by bark beetles every year, which negatively affects the numbers and the quality of trees. Untimely processing of the trees leads to their drying and destruction. According to modern systematics, bark beetles belong to the Scolytinae (Latreille, 1804) subfamily of the Curculionidae (Latreille, 1802) family. There are about 6,000 species of bark beetles from 28 triba and 230 genera in the world [8]. These insects also cause serious damage in countries neighboring of Azerbaijan [1, 2, 9, 11 ]. Despite the fact that bark beetles are of great agricultural importance, they are not sufficiently studied in Azerbaijan. Materials and Methods.The material for research was collected and treated according to common entomological methods. The vegetative organs of various trees were cut and dissected to detect adult beetles, eggs and larvae of bark beetles. Identification of bark beetles was carried out according to keys. MBS-9 microscope was used to determine the morphological features of beetles. Results. As a results of the research, we analyzed 241 samples (237 adults and 4 pupae) of bark beetles collected in 7 districts of the southern slopes of the Greater Caucasus, of which 54 specimens belonged to Scolytus mali and 187 to Hypoborus ficus. Conclusion. Out of 30 species of bark beetles detected on the southern slopes of the Greater Caucasus, 7 ones (Scolytus mali Bechst., S. amygdali Guer., S. fasciatus Rtt., S. rugulosus Ratz., Hypoborus ficus Er., Xyleborus dispar F., X. saxeseni Ratz.) were determined as fruit trees pests. Two of them (Scolytus mali and Hypoborus ficus) are widely distributed in the area and cause serious damage to fruit trees.

Exposure to low concentrations of pesticide stimulates ecological functioning in the dung beetle Onthophagus nuchicornis

Body-size is an important trait for predicting how species contribute to ecosystem functions and respond to environmental stress. Using the dung beetle Onthophagus nuchicornis (Coleoptera: Scarabaeidae), we explored how variation in body-size affected ecosystem functioning (dung burial) and sensitivity to an environmental stressor (exposure to the veterinary anthelmintic ivermectin). We found that large beetles buried nearly 1.5-fold more dung than small beetles, but that mortality from exposure to a range of concentrations of ivermectin did not differ between large and small beetles. Unexpectedly, we found that exposure to low concentrations of ivermectin (0.01⁠–1 mg ivermectin per kg dung) stimulated dung burial in both small and large beetles. Our results provide evidence of ecological functioning hormesis stemming from exposure to low amounts of a chemical stressor that causes mortality at high doses.

Perching Behavior by Dung Beetles (Coleoptera: Scarabaeidae): A Spatial Segregation Mechanism to Dilute Interspecific Competition in Highly Rich Assemblages?

AbstractSit-and-wait is a common strategy to optimize time and energy devoted to foraging activities. Among Coleoptera, dung beetles are one of the groups that display this behavior. Although diverse aspects of natural history have been reviewed, no agreement exists on which theory may explain this food searching tactic. We performed a systematic literature review about this behavior in dung beetles, analyzing existing studies, and discussing potential explanations. We identified six different hypotheses (resource partitioning, food detection, foraging time, predator’s avoidance, thermoregulation, and resting). Based on the evidence that we found, we support the hypothesis that the main driver of perching behavior is a strategy of spatial segregation. We found reports for several tribes in different biogeographical regions, especially in Neotropical forests. Few studies explore the relationship between perching height and dung beetles’ size. However, recent findings sustained that dung beetles perch at a height proportional to its size, large beetles prefer bigger leaves, and functional groups perch at different heights. Dung beetles observed perching were strictly coprophagous and there is no specific relationship between dial activity and perching behavior. We also found perching records of the three main functional guilds (tunnelers, rollers, and dwellers). Despite several studies of dung beetles perching, there is a lack of experimental analyses. One aspect to analyze in future investigations is the relationship between perching behavior and functional traits. Finally, it is essential to explore and solve some questions that we propose to understand the functional role of this behavior in the structure of assemblages.