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Atlantic Bluet



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Enallagma doubledayi

Selys, 1850


Order Odonata
Suborder Zygoptera
Superfamily Coenagrionoidea
Family Coenagrionidae
Genus Enallagma
Species doubledayi (Selys, 1850) [Agrion]


Identification

The front of the head of the male is mostly blue with an anteriorly rounded black stripe. The top is largely black with the pale blue postocular spots narrow and elongated. A pale occipital bar separates them, but is rarely confluent with them. The middorsal thoracic carina is black with at most a hint of blue at its upper end. The black middorsal stripe is slightly less than half the width of the mesepisterna. The blue antehumeral stripe is 1/2 -2/3 the width of the middorsal stripe and the black humeral stripe is nearly equal in width to the antehumeral stripe. The rest of pterothorax is blue fading markedly towards the underside. The legs and coxae are largely pale blue to tan with broad black stripes on the femora and tibiae. The tarsi are tan. The abdomen is blue and segment 1 has a basal black spot on the dorsum that extends posterolaterally. Segment 2 is black on the dorsoapical 1/2 of the segment. A black apical band extends for approximately a fifth the length of segments 3-5. The black stripe on segment 6 is more extensive, tapering anteromedially to 3/4 the length of the segment. Segment 7 is black dorsally for its entire length, except for a narrow apical and sometimes basal pale ring. Segments 8-9 are blue with a small apical and basal spot on the dorsum of 8. The dorsum of segment 10 is black and strongly emarginated laterally. The cerci are black and half or more the length of segment 1 0. Each has a distinct pale apical tubercle when viewed laterally. Dorsally, the upper arm is distinctly wider than tubercle. The paraprocts are pale with black tips and extend 2/3-3/4 the length of the cerci. The paraprocts are broad basally, terminating rather bluntly. The female may either be pale brown, green, or blue. The general color pattern is similar to the male. The middle prothoracic lobe lacks distinct pits. The mesostigmal plates bear a distinct posterior border. The medial third of each plate is bordered by distinct narrow ridge. The plates themselves are rather rectangular with an oval depression medially. The Pterothorax, wings, and legs are all generally like those of the male. The black stripes on the abdomen are more extensive. The stripe on segment 1 reaches apically for 3/4 the length of the segment. The remaining segments, 2-10, all bear a full-length black stripe, pale medial ring, and a medially interrupted basal ring.

Size

Total length: 28-37 mm; abdomen: 22-30 mm; hindwing: 16-21mm.

Similar Species

Familiar Bluet (E. civile ) is very similar, but the black markings on the abdomen are slightly more extensive on Atlantic Bluet. These two species have been taken together, though Familiar Bluet is far more abundant and widespread in the south-central United States. There is a very good chance that this species has been frequently overlooked in our region because of its similarity to the very ubiquitous Familiar Bluet. Carefully examine the male caudal appendages and female mesostigmal plates to tell these two species apart. Also, compare with the similar species listed under Familiar Bluet.

Habitat

Newly formed or ephemeral ponds and lakes, and occasionally sluggish streams.

Discussion

Atlantic Bluet is known west of the Mississippi only by a couple of collections from north central Texas. This appears to be a dramatic range extension based on previous collections, but it may occur in isolated populations eastward to the Mississippi River and simply have be en overlooked because of its similarly to Familiar Bluet. Atlantic Bluet shows some tolerance to saline waters along the coast, but is most typically found in sandy-bottomed new or ephemeral ponds. Males can generally be seen conspicuously perched on riparian vegetation at the water's edge. Pairs mate on emergent vegetation and females lay eggs in tandem. The female will remain underwater, laying eggs after pulling free from the male, for only a few minutes at a time. Males remain perched nearby, guarding the female. Leafhoppers are a common prey of Atlantic Bluet.

Distribution

Eastern U.S. from Florida to Pennsylvania west to Texas; also Cuba and Jamaica.