Enallagma exsulans

(Hagen, 1861)

Stream Bluet

Enallagma exsulans, commonly known as the Stream Bluet, is a of in the Coenagrionidae. It is distinguished from many other bluet species by its strong association with flowing water rather than still ponds and lakes. The species ranges across much of eastern and central North America.

Enallagma exsulans by (c) Sam Kieschnick, some rights reserved (CC BY), uploaded by Sam Kieschnick. Used under a CC-BY license.Enallagma exsulans by the Smithsonian. Used under a CC0 license.Stream Bluet (Enallagma exsulans) by D. Gordon E. Robertson. Used under a CC BY-SA 3.0 license.

Pronunciation

How to pronounce Enallagma exsulans: //ɛnˈæl.əɡ.mə ɛkˈsuː.lænz//

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Identification

Distinguished from other bluet (Enallagma spp.) primarily by preference for moving water. Differs from the Familiar Bluet (E. civile) and other pond-dwelling by its occurrence along streams and rivers. Lacks the blue-tipped common in many . Identification to species level typically requires examination of male terminal appendages.

Images

Appearance

measure 29–37 mm in length. Like other bluet , males typically exhibit blue coloration on the . The lacks the blue abdominal tip found in many other Enallagma species. Overall body form is slender with narrow, transparent wings held together above the body when at rest.

Habitat

Most commonly found along small to medium-sized rivers and streams with moderate current. Occasionally occurs at lake margins. Associated with vegetated shorelines where perch on emergent vegetation.

Distribution

Eastern and central North America. Present in the United States and Canada, with records from Vermont and throughout much of the ' range.

Diet

are aerial capturing small flying insects. Larvae are aquatic predators feeding on small including mosquito larvae.

Life Cycle

Hemimetabolous development with aquatic larval stage (naiad) and terrestrial stage. are deposited on submerged aquatic vegetation; females may submerge completely to oviposit. Larval development occurs in flowing water.

Behavior

perch on vegetation near water, often hanging from stems. Males and females fly in tandem during mating; males release females when females submerge to deposit . Adults are active fliers that hunt prey on the wing.

Ecological Role

and larvae function as in aquatic and riparian . Larvae may serve as indicators of stream health.

Similar Taxa

  • Enallagma civileFamiliar Bluet is similar in appearance but prefers ponds and lakes rather than flowing water; also typically has blue-tipped
  • Other Enallagma speciesMany overlap in coloration but differ in preference (still water vs. streams) and male terminal appendage

More Details

Taxonomic history

described by Hagen in 1861; originally placed in Agrion. Rosser Garrison published a taxonomic revision of the genus Enallagma in 1984 that included this species.

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Sources and further reading