How to train your dragon: absolute conditioning in larval dragonflies.

Insects, despite possessing relatively small brains, exhibit noteworthy adaptive behaviors, making them intriguing subjects for understanding learning mechanisms. This study explores the learning capabilities of dragonfly larvae (Anisoptera: Aeshnidae) in conditioning experiments, shedding light on the cognitive processes that underpin their remarkable abilities. As apex predators, dragonflies play a crucial role in ecosystems, necessitating a diverse range of learning behaviors for survival and reproductive success. We addressed whether dragonfly larvae can differentiate between different colored stimuli and associate color with prey. Our experimental design demonstrated that dragonfly larvae are able to recognize conditioning stimuli. The findings contribute valuable insights into the cognitive abilities of dragonflies, suggesting that these insects can learn and discriminate colors of stimuli. Overall, this research broadens our understanding of insect learning and cognition, contributing to the broader field of animal behavior and memory.

Ontogenetic colour change of a sexual ornament in males of a damselfly: female mimicry, crypsis or both?

Female mimicry by males is a widespread phenomenon in several taxa and may be involved in aggression avoidance or facilitated access to resources. In early developmental stages, female mimicry may be a mechanism involved in signalling sexual immaturity or, when coupled with strategies related to visual camouflage, may be involved in the avoidance of male-male agonistic interactions. Here, we addressed whether the delayed colour maturation of a sexual ornament in males of Mnesarete pudica damselflies might be a case of crypsis, female mimicry or both. We analysed how conspecifics and predators perceive the pigmented wings of juvenile males by contrasting the wing spectra against a savannah background and the wings of both juvenile and sexually mature males and females. Our results based on the modelled visual system of conspecifics and predators suggest that the colour maturation of juvenile males may function as both crypsis and female mimicry. We discuss whether these results related to age- and sexual-dichromatism might be a mechanism to avoid unwanted intraspecific interactions or to avoid territorial and aggressive males. We conclude that the female mimicry and crypsis in juvenile males of M. pudica are mechanisms involved in avoidance of predators and unwanted intraspecific interactions, and the signalling of sexual maturity.

Color lightness of velvet ants (Hymenoptera: Mutillidae) follows an environmental gradient.

Color traits are highly influenced by environmental conditions along the distributional range of many species. Studies on the variation of animal coloration across different geographic gradients are, therefore, fundamental for a better understanding of the ecological and evolutionary processes that shape color variation. Here, we address whether color lightness in velvet ants (Hymenoptera: Mutillidae) responds to latitudinal gradients and bioclimatic variations, testing three ecogeographic rules: The Thermal melanism hypothesis; the Photoprotection hypothesis; and Gloger's rule. We test these hypotheses across the New World. We used photographs of 482 specimens (n = 142 species) of female mutillid wasps and extracted data on color lightness (V). We analyzed whether variation in color is determined by bioclimatic factors, using Phylogenetic Generalized Least Square analysis. Our explanatory variables were temperature, ultraviolet radiation, humidity, and forest indicators. Our results were consistent with the Photoprotection hypothesis and Gloger's rule. Species with darker coloration occupied habitats with more vegetation, higher humidity, and UV-B radiation. However, our results refute one of the initial hypotheses suggesting that mutillids do not respond to the predictions of the Thermal melanism hypothesis. The results presented here provide the first evidence that abiotic components of the environment can act as ecological filters and as selective forces driving the body coloration of velvet ants. Finally, we suggest that studies using animals with melanin-based colors as a model for mimetic and aposematic coloration hypotheses consider that this coloration may also be under the influence of climatic factors and not only predators.

The unusual tracheal system within the wing membrane of a dragonfly.

Some consider that the first winged insects had living tissue inside the wing membrane, resembling larval gills or developing wing pads. However, throughout the developmental process of the wing membrane of modern insects, cells and tracheoles in the lumen between dorsal and ventral cuticle disappear and both cuticles become fused. This process results in the rather thin rigid stable structure of the membrane. The herewith described remarkable case of the dragonfly Zenithoptera lanei shows that in some highly specialized wings, the membrane can still be supplemented by tracheae. Such a characteristic of the wing membrane presumably represents a strong specialization for the synthesis of melanin-filled nanolayers of the cuticle, nanospheres inside the wing membrane and complex arrangement of wax crystals on the membrane surface, all responsible for unique structural coloration.

Variable assessment of wing colouration in aerial contests of the red-winged damselfly Mnesarete pudica (Zygoptera, Calopterygidae).

Wing pigmentation is a trait that predicts the outcome of male contests in some damselflies. Thus, it is reasonable to suppose that males would have the ability to assess wing pigmentation and adjust investment in a fight according to the costs that the rival may potentially impose. Males of the damselfly Mnesarete pudica exhibit red-coloured wings and complex courtship behaviour and engage in striking male-male fights. In this study, we investigated male assessment behaviour during aerial contests. Theory suggests that the relationship between male resource-holding potential (RHP) and contest duration describes the kind of assessment adopted by males: self-assessment, opponent-only assessment or mutual assessment. A recent theory also suggests that weak and strong males exhibit variations in the assessment strategies adopted. We estimated male RHP through male body size and wing colouration (i.e. pigmentation, wing reflectance spectra and transmission spectra) and studied the relationship between male RHP and contest duration from video-documented behavioural observations of naturally occurring individual contests in the field. The results showed that males with more opaque wings and larger red spots were more likely to win contests. The relationships between RHP and contest durations partly supported the self-assessment and the mutual assessment models. We then experimentally augmented the pigmented area of the wings, in order to evaluate whether strong and weak males assess rivals' RHP through wing pigmentation. Our experimental manipulation, however, clearly demonstrated that strong males assess rivals' wing pigmentation. We finally suggest that there is a variation in the assessment strategy adopted by males.

Last instar larva of the critically endangered Oxyagrion franciscoi Machado & Bede, 2016 (Odonata: Coenagrionidae) from Serra da Canastra National Park.

Oxyagrion franciscoi Machado & Bede, 2016 is a critically endangered damselfly species endemic to the Serra da Canastra National Park, Brazil, a vital environmental reserve within the Cerrado hotspot for biodiversity conservation. Here we reared, illustrated, and described the last instar larva of O. franciscoi.

Vector species richness predicts local mortality rates from Chagas disease.

Vector species richness may drive the prevalence of vector-borne diseases by influencing pathogen transmission rates. The dilution effect hypothesis predicts that higher biodiversity reduces disease prevalence, but with inconclusive evidence. In contrast, the amplification effect hypothesis suggests that higher vector diversity may result in greater disease transmission by increasing and diversifying the transmission pathways. The relationship between vector diversity and pathogen transmission remains unclear and requires further study. Chagas disease is a vector-borne disease most prevalent in Brazil and transmitted by multiple species of insect vectors of the subfamily Triatominae, yet the drivers of spatial variation in its impact on human populations remain unresolved. We tested whether triatomine species richness, latitude, bioclimatic variables, human host population density, and socioeconomic variables predict Chagas disease mortality rates across over 5000 spatial grid cells covering all of Brazil. Results show that species richness of triatomine vectors is a good predictor of mortality rates caused by Chagas disease, which supports the amplification effect hypothesis. Vector richness and the impact of Chagas disease may also be driven by latitudinal components of climate and human socioeconomic factors. We provide evidence that vector diversity is a strong predictor of disease prevalence and give support to the amplification effect hypothesis.

Total environment sentinels: Dragonflies as ambivalent/amphibiotic bioindicators of damage to soil and freshwater.

Discerning the impact of anthropogenic impacts requires the implementation of bioindicators that quantify the susceptibilities and vulnerabilities of natural terrestrial and aquatic ecosystems to perturbation and transformation. Although legal regulations in Brazil recognize the value of bioindicators in monitoring water quality, the depreciation of soil conditions has yet to receive adequate attention. Thus, our study aimed to evaluate the potential of odonates (dragonflies and damselflies) as amphibiotic bioindicators to reflect the correlation between the degradation of aquatic and terrestrial habitats in pasture-dominated landscapes. We assessed the relationship between the biotic indices of Odonata and the conservation status of preserved riparian landscapes adjacent to anthropogenically altered pastures in 40 streams in the Brazilian savannah. Our results support the hypothesis that Odonata species composition may be a surrogate indicator for soil and water integrity, making them promising sentinels for detecting environmental degradation and guiding conservation strategies in human-altered landscapes. Importantly, while the Zygoptera/Anisoptera species ratio is a useful bioindicator tool in Brazilian forest, it is less effective in the open savannah here, and so an alternative index is required. Importantly, while the Zygoptera/Anisoptera species ratio is a useful bioindicator tool in Brazilian forest, it is less effective in the open savannah here, and so an alternative index is required. On the other hand, our results showed the Dragonfly Biotic Index to be a suitable tool for assessing freshwater habitats in Brazilian savannah. We also identified certain bioindicator species at both ends of the environment intactness spectrum.

Systematic challenges and opportunities in insect monitoring: a Global South perspective.

Insect monitoring is pivotal for assessing biodiversity and informing conservation strategies. This study delves into the complex realm of insect monitoring in the Global South-world developing and least-developed countries as identified by the United Nations Conference on Trade and Development-highlighting challenges and proposing strategic solutions. An analysis of publications from 1990 to 2024 reveals an imbalance in research contributions between the Global North and South, highlighting disparities in entomological research and the scarcity of taxonomic expertise in the Global South. We discuss the socio-economic factors that exacerbate the issues, including funding disparities, challenges in collaboration, infrastructure deficits, information technology obstacles and the impact of local currency devaluation. In addition, we emphasize the crucial role of environmental factors in shaping insect diversity, particularly in tropical regions facing multiple challenges including climate change, urbanization, pollution and various anthropogenic activities. We also stress the need for entomologists to advocate for ecosystem services provided by insects in addressing environmental issues. To enhance monitoring capacity, we propose strategies such as community engagement, outreach programmes and cultural activities to instill biodiversity appreciation. Further, language inclusivity and social media use are emphasized for effective communication. More collaborations with Global North counterparts, particularly in areas of molecular biology and remote sensing, are suggested for technological advancements. In conclusion, advocating for these strategies-global collaborations, a diverse entomological community and the integration of transverse disciplines-aims to address challenges and foster inclusive, sustainable insect monitoring in the Global South, contributing significantly to biodiversity conservation and overall ecosystem health. This article is part of the theme issue 'Towards a toolkit for global insect biodiversity monitoring'.

Argia koroivarum sp. nov. (Odonata: Coenagrionidae) from Minas Gerais state, Southeastern Brazil.

Argia koroivarum sp. nov. (BRAZIL, Minas Gerais state, São Roque de Minas, Parque Nacional Serra da Canastra, 9.iv.2019, (-20.2323, -46.6084, 1306m asl), D.S. Vilela, R. Guillermo, R. Koroiva leg., Laboratory of Ecological Studies on Ethology and Evolution (LESTES), Uberaba, Minas Gerais State, Brazil) is described, illustrated, and diagnosed based on specimens collected in Minas Gerais state, Brazil. The new species can be diagnosed from its congeners by the morphology of male ligula, dorsal branch of paraproct, and of female mesostigmal lobes.

Scorpion envenomation in the neotropical savannah: Environmental predictors and years of lost life.

Scorpion stings envenomation (SSE) is a growing medical concern in Brazil, particularly in the state of Minas Gerais, which has recorded a significant number of incidents. This study aimed to investigate the potential predictors of scorpion sting incidence and evaluate the cost-effectiveness of interventions in Minas Gerais. Generalized Estimating Equations (GEE) models were constructed using socioeconomic and environmental variables as predictors and scorpion sting incidence as the response variable. The analysis revealed that mean annual temperature and major land use type were significant predictors of scorpion sting incidence, while precipitation and socioeconomic variables showed no relationship with incidence. The total number of cases and annual incidence of scorpion stings overlapped with regions experiencing higher forest conversion and agricultural land use, as well as higher temperatures. The estimated Disability-Adjusted Life Years (DALY) for scorpion sting incidents in Minas Gerais was substantial, indicating the need for effective prevention and treatment measures. The cost per DALY averted varied among municipalities, with some requiring minimal investment while others needing significant funding to address the scorpion risk. Mean annual temperature emerged as the main risk factor for scorpion stings, contributing to increased costs associated with antivenom treatment. These findings highlight the importance of considering environmental factors and implementing targeted interventions to mitigate scorpion sting incidents and reduce associated morbidity and mortality.

A new species of Gomphoides Selys, 1854 (Odonata: Gomphidae) from the Environmental Protection Area of the Uberaba River, Brazil.

A new species of the Neotropical dragonfly genus Gomphoides Selys, 1854 (Odonata: Gomphidae) is erected from the Cerrado of central Brazil, distinguished by epiproct morphology, body coloration and wing venation. Gomphoides davi Datto-Liberato Guillermo-Ferreira sp. nov. resembles G. perdita (Frster, 1914), but is distinguished from it by the S10 black, while it is yellow in G. perdita; four cells in the subtriangle of Fw while there are three cells in G. perdita and epiproct shorter than half of the length of cerci while epiproct is more than half the length of the cerci in G. perdita. We also provide additional information for other Gomphoides species. The discovery of a new species in the Environmental Protection Area of the Uberaba River, Minas Gerais, raises concern for the conservation of the biodiversity of the area, mainly because of recent threats due to cattle herding and agriculture.

Detecting Darwinian Shortfalls in the Amazonian Odonata.

Among the oldest winged insects, odonates are a monophyletic order that have become important models for ecological studies because of their highly diverse reproductive behaviors and their role as top predators and bioindicators. However, knowledge on evolutionary relationships within the order is still scarce compared to other taxa, and this situation is even more complicated in areas with high biodiversity, such as in the Amazon. Here, we sought to identify knowledge gaps on Amazonian Odonata regarding three main aspects: (i) how the inclusion of Amazonian taxa affects our interpretation of the evolutionary relationships of Zygoptera and Anisoptera; (ii) the position of Amazonian taxa in the existing supertree of the Odonata; (iii) dating evolutionary divergence between nodes using fossil records; (iv) assessing whether more species-rich basins (e.g., Amazon basin) have a larger phylogenetic gap when compared to basins with lower richness in South and Central America; and (v) in the light of our knowledge, we discuss diversification patterns found in the most predominant clades of Amazonian taxa. We built a supertree from currently available phylogenetic information of Odonata. The results show that there is no genetic information for 85% (n: 503) of the Amazonian species and that family level relationships are unknown for 17 genera. After compiling the data, we observed that clades belonging to Neotropical lineages are the most poorly resolved, with large polytomies. This problem was identified in many Anisoptera genera, such as Macrothemis, Dasythemis, Elasmothemis, and Erythrodiplax. Our results also suggest that not always the richest basins have the greatest phylogenetic gaps. As expected, we found important gaps in the existing Odonata phylogenies, especially in clades that include Amazonian representatives, that are also those less known from ecological and conservation perspectives.

Heteragrion/ gorbi/ sp. nov. (Odonata: Heteragrionidae) from southeastern Brazil.

Heteragrion gorbi sp. nov. (Zygoptera: Heteragrionidae) is described and diagnosed based on six ♂♂ and one ♀. The specimens were collected in a stream in a Neotropical savannah fragment in São Carlos, São Paulo, Brazil. We present pictures of the holotype and the female. This is a species with blue coloration pattern, rare among its congeners.

Do latitudinal and bioclimatic gradients drive parasitism in Odonata?

Prevalence of parasites in wild animals may follow ecogeographic patterns, under the influence of climatic factors and macroecological features. One of the largest scale biological patterns on Earth is the latitudinal diversity gradient; however, latitudinal gradients may also exist regarding the frequency of interspecific interactions such as the prevalence of parasitism in host populations. Dragonflies and damselflies (order Odonata) are hosts of a wide range of ecto- and endoparasites, interactions that can be affected by environmental factors that shape their occurrence and distribution, such as climatic variation, ultraviolet radiation and vegetation structure. Here, we retrieved data from the literature on parasites of Odonata, represented by 90 populations infected by ectoparasites (water mites) and 117 populations infected by endoparasites (intestinal gregarines). To test whether there is a latitudinal and bioclimatic gradient in the prevalence of water mites and gregarines parasitizing Odonata, we applied Bayesian phylogenetic comparative models. We found that prevalence of ectoparasites was partially associated with latitude, showing the opposite pattern from our expectations - prevalence was reduced at lower latitudes. Prevalence of endoparasites was not affected by latitude. While prevalence of water mites was also positively associated with vegetation biomass and climatic stability, we found no evidence of the effect of bioclimatic variables on the prevalence of gregarines. Our study suggests that infection by ectoparasites of dragonflies and damselflies is driven by latitudinal and bioclimatic variables. We add evidence of the role of global-scale biological patterns in shaping biodiversity, suggesting that parasitic organisms may prove reliable sources of information about climate change and its impact on ecological interactions.

New Species of Entypus (Hymenoptera: Pompilidae) and notes on the natural history of some Atlantic Forest spider wasps.

We describe the new species Entypus renata, sp. nov., from the Brazilian Atlantic Forest and report on its host. We also provide the first host records for Ageniella (Priophanes) erythroptera (Banks), Entypus bituberculatus (Gurin-Meville) and an undetermined species of Poecilopompilus Ashmead. In addition, we report behavioral aspects for these species, including a new ethological sequence for Poecilopompilus.

Females of the red damselfly Mnesarete pudica are attracted to more ornamented males and attract rival males.

Male calopterygid damselflies often exhibit colourful wings used during aggressive contests and courtship displays. Evidence suggests that male wing coloration is a secondary sexual character assessed by males and females to identify male quality. In some species, males adopt a lekking strategy, where females visit exhibition arenas and choose the best mate. Here, we addressed whether the behaviour of Mnesarete pudica males is influenced by female visitation when gathering in leks. We hypothesized that female visitation would increase male investment in courtship and fighting, while reducing patrolling flights and harassment attempts. Moreover, we tested the hypothesis that more ornamented males attract more females to the territory, following the hotshot model of lek evolution. Our results suggest that, indeed, males with more pigmented wings attract more visiting females, independently of male size. Our results also show that the number of females in a territory attracts more males and elicits male contest behaviour, reducing male harassment. We conclude that male ornament and male clustering is a good predictor of female visitation rates, suggesting that females may exert mate choice.

The female of Epipleoneura spatulata Rácenis, 1960 (Odonata: Protoneurinae).

Here we describe the hitherto unknown female of Epipleoneura spatulata Rácenis, 1960 and present a table of characters (all illustrated) to distinguish it from other known congeneric females. We suggest that the main diagnostic character of the female of E. spatulata is the shape of posterior margin of prothorax, which is flat medially with smoothly curved erect lateral projections.

Revision of the genus Minagrion Santos, 1965 (Odonata: Coenagrionidae).

Endemic to Brazil, the genus Minagrion Santos, 1965 is revised for the first time. The genus contains five species, and here we establish diagnostic characters, keys and drawings for both sexes. Furthermore, we propose the synonymy of M. franciscoi Machado Bedê, 2015 new syn. with M. caldense Santos, 1965.

The female of Heteragrion icterops Selys, 1862 (Odonata: Heteragrionidae) with comments and key on the Brazilian females of Heteragrion group B.

The female of Heteragrion icterops Selys, 1862, incompletely mentioned in 1886, is described, illustrated, keyed and diagnosed based on specimens collected in Pará State, North Brazil. We also provide an identification key and diagnostic comments on other two Group B females occurring in Brazil: H. angustipenne Selys, 1886 and H. bariai De Marmels, 1989. Heteragrion icterops females can be distinguished from other female congeners by having the genital valves tips leveling the posterior margin of S10 and by the morphology of the intersternites, presenting a well-developed dorsal plate and lacking a posterior plate.