Libellula is a genus of dragonflies, called chasers (in English) or skimmers (in American), in the family Libellulidae. They are distributed throughout the temperate zone of the Northern Hemisphere. Many have showy wing patterns and bright bodies.
These are medium to large dragonflies, in length. The faces of these dragonflies can be white, yellow, red, brown, or black. Their bodies can be light yellow, orange, red, or brown, and the males often have a glaucous or pruinose coating when mature. Wings in the genus Libellula often have yellow, orange, or brown patterns, or they can be completely clear.
Unique characteristics belonging only to the genus Libellula are not well defined. Many species or individual dragonflies have variations of these identifying traits. However, four synapomorphies are described, with two of them referring to the wing venation. The other two identifying features of the genus Libellula are a characteristic brown area at the base of the forewing and a wide abdomen.
Libellula dragonflies are generally distributed in the Northern Hemisphere. A few species are endemic to Europe and Asia, but much of the diversity of this genus in North America. L. herculea is the only species with an extensive distribution in South America.
Adult Libellula are commonly found near bodies of water, perching or landing on reeds and branches. Larvae of the genus live exclusively in water, particularly in the muddy bottoms of still or slow-moving water bodies. Some species, like L. pulchella, can live in drinking tanks of well-water for cattle, along with their natural habitat of ponds and marshes.
Of the 28 species in the genus, five are currently listed on the IUCN Red List as threatened with extinction. L. angelina is listed as critically endangered, L. coahuiltecana is endangered, and L. jesseana is vulnerable. The other two species, L. mariae and L. pontica, are listed as near threatened.
Eggs are laid by adult females directly into water bodies, which will hatch into aquatic nymphs. Libellula nymphs can compete for resources with other nymphs in their genus in a shared habitat. These nymphs will also show cannibalism on each other in high densities, and dragonflies are often the top predator in fishless water bodies. Species within Libellula are efficient predators, using mechanical and visual cues to release their developed labium and labial palpi to catch their prey.
Adult males in the genus Libellula can be territorial and aggressive. The territories they defend are ideal breeding sites, which are in sunlight and lacking surface vegetation. They fly around their territory and attack other male dragonflies to eliminate mating competition. The males are likely territorial due to the sex-ratio being biased towards males, meaning that there are more males than females.
The genus name comes from Latin ', meaning "a carpenter's level", because of the insect's ability to stay level when hovering.
The type species is Libellula depressa Linnaeus, 1758, designated by William Forsell Kirby in 1889. Some subsequent authors have cited Libellula quadrimaculata as the type, but this contravenes the principle of priority.
The taxa Ladona (corporals) and Plathemis (whitetails) have been considered as synonyms of Libellula, subgenera, or separate genera by different authorities. Some phylogenetic analysis using 16S rRNA sequence data and insect morphology has supported their status as subgenera of Libellula rather than independent genera; however, the World Odonata List retains these as distinct genera.
List of the 28 species accepted by the World Odonata List: