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Dynamic signals are a widespread phenomenon in several taxa, usually associated with intraspecific communication. In contrast, dynamic iridescent signals are detectable only at specific angles of illumination; hence, the animal can hide the signal to avoid detection when necessary. This structural coloration is mostly dependent on the illumination, the contrast against the background and the vision of the receiver. Complex behavioural displays can be coupled with structural coloration to create dynamic visual signals that enhance these functions. Here, we address whether iridescence of the males of a damselfly that inhabits dark rainforests, Chalcopteryx scintillans, can be considered a dynamic visual signal. We analyse whether coloration is perceived by conspecifics, while reducing detectability to eavesdroppers against three types of backgrounds. Our results suggest that the visual background affects the detectability of male hindwings by different receivers, mostly predators and prey. We discuss whether these results and the angle dependence of colour could indicate a mechanism to avoid unwanted intraspecific interactions or even to lure both predators and prey. We conclude that the main functions of the dynamic iridescent signal are to communicate with conspecifics while hindering the signal for prey, adding evidence of the multifunctionality of structural coloration coupled with behavioural displays in animals.

Adult odonates (dragonflies and damselflies) exhibit a great diversity of colors which vary remarkably between species, between individuals within species, and throughout the individual's lifetime in some species. Here, we provide a summary of what is known about color recognition, and production of color including pigmentary absorption, structural reflectance, and fluorescence, in odonates. We also review the current understanding of the function of color in adult odonates, such as in signals during mate choice, in species recognition, and in predator avoidance, as well as in physiological adaptations to abiotic conditions. Finally, we provide some directions for future research: eye and pterostigma color, coloration at different life stages, UV color, phylogenetic analysis of color evolution, color and hot climate patterns, and standardization of color recordings. Given how easily they can be marked and tracked, odonates are exemplary animals for field and laboratory research. Therefore, unraveling the physiology, evolution, and ecology of odonate color can provide significant advances, in general, to understand insect color.

Bright iridescent colours are widespread in several aquatic and terrestrial animal taxa and are usually involved in intraspecific communication and/or predator avoidance. Camouflage by iridescence may be one strategy to avoid predators when the animal exhibits bright colours that match the brightness of its surroundings. Hence, animal structural colouration may have a "brightness matching" or "counterbrightness" function when observed against bright or glossy backgrounds. Here, we addressed the role of such counter-brightness effect of the iridescent wings of the Morpho dragonfly Zenithoptera lanei for avoiding detection. We hypothesized that the bright reflectance of the dragonfly wings is cryptic against the bright water surface and the glossy vegetation where they naturally occur, protecting the dragonfly from visually oriented predators, deceiving prey and signalling to conspecifics when desired. We addressed whether (1) the iridescent colours of Z. lanei wings function as a visual strategy to reduce their wing detectability by brightness matching the background and (2) the detectability of wings against vegetation and water varies according to the observer. For this, we modelled how conspecifics, dipteran prey and predatory birds see the odonate wings against the vegetation of the Neotropical Savannah and against the water surface where the dragonflies perch. Our results suggest that Z. lanei dragonflies can avoid detection by predators, prey and conspecifics when perched on their natural habitats (i.e., ponds) against the bright background of the water surface. Here, we add evidence to the multifunctionality of structural colours in animals and the function of iridescence in camouflage. The bright iridescence and ultraviolet reflective nanostructures of Z. lanei wings when coupled with striking behavioural displays may provide a dynamic and safe intraspecific communication channel.

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.

Recent expeditions to the Serra da Canastra and Chapada dos Guimarães National Parks in Brazil resulted in the collection of larvae of Argia mollis Hagen in Selys, 1865 and A. smithiana Calvert, 1909. Thus, here we describe the last instar larvae of these two Argia species from the Brazilian Cerrado.

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Neocordulia is a Neotropical genus with 16 species distributed in the South and Central Americas. To date, only seven larvae of this genus have been described. Here we describe the final instar larva of Neocordulia volxemi (Selys, 1874), collected in the Environmental Protection Area of the Uberaba River Basin in the State of Minas Gerais, Brazil. The metallic–green adults were found flying in a forested area in a Conservation Unit, while the larvae were found in a waterfall and surrounding rocky walls. The Cerrado remnant area is currently threatened by degraded pastures and increasing areas of monoculture agriculture.