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Burgundy Bluet



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Enallagma dubium

Root, 1924


Order Odonata
Suborder Zygoptera
Superfamily Coenagrionoidea
Family Coenagrionidae
Genus Enallagma
Species dubium Root, 1924 [Enallagma]


Identification

The male has deep red eyes that become pale brown with age. The face is orange-red to violet and the rest of the head is black with metallic reflections. The middorsal thoracic carina and stripe are black with metallic purple or blue-green luster. The antehumeral stripe is orange-red and no more than a quarter the width of the middorsal stripe. The broad humeral stripe is black with metallic reflections and nearly equal in width to the middorsal stripe. The upper end of the humeral stripe is confluent with the short black stripe of the interpleural stripe. Occasionally, a small isolated spot is present anterior to the stripe. The black stripe, at its widest, is equal in width to the antehumeral stripe. The area between the humeral and metapleural stripes is orange. The rest of the pterothorax is lighter, fading to yellow ventrally. The legs are orange-red, becoming paler distally. Occasionally, there is a black stripe evident on th e femora. The tarsi are pale armed with black spurs. The abdomen is orange-red and black. The entire dorsum is uniformly black with only a narrow apical ring on segment 1 and basal rings on segments 3-7. The lateral pale areas are orange-red basally, fading to yellow on the distal segments. Occasionally, there are pale apical rings evident on segments 7-9. The cerci are black laterally and pale medially; generally as long as, if not slightly longer than, segment 10. There is a distinct ventrally projecting tooth at its midlength. The pale paraprocts are no more than half the length of the cerci. They are dark apically and project slightly posteroventrally. The female is paler, with more orange-yellow or tan and generally lacks any hint of metallic reflection in the black areas, as opposed to the male; otherwise, similar in pattern to the male. The middle lobe of the pronotum bears large, distinctive pits near its anterior edge. The mesostigmal plates are noticeably triangular in shape, each having a prominent posteromedial tubercle and deeply depressed forming a distinct posterior border for most of their distance laterally. There is a prominent tubercle immediately posterior to each mesostigmal plate on the mesepisternum. The abdomen is similar to the male, but with the pale apical rings on segments 7-9 often lacking.

Size

Total length: 25-30 mm; abdomen: 20-25 mm; hindwing: 12-17 mm.

Similar Species

Orange Bluet (E. signatum ) is larger and lacks the dark stripe on the metapleural suture. Cherry Bluet (E. concisum ) is also similar, but has a pair of pale spots on the the prothorax, an area that is all black in Burgundy Bluet.

Habitat

Heavily vegetated black water ponds, lakes, oxbows, sloughs and slow reaches of streams, often associated with lily pads.

Discussion

Burgundy Bluets seems to be locally restricted, west of the Mississippi River, to the Caddo Lake, southeastern piney woods and Big Thicket Region of eastern Texas and southeastern Oklahoma. It is infrequently encountered in these areas. Burgundy Bluet is generally found in areas where lily pads are abundant. It has been noted that this species can become amazingly inconspicuous, seemingly disappearing, as they enter shaded areas while patrolling. Mating pairs can be seen from midday into the afternoon on floating vegetation. Pairs prefer to lay eggs through holes in water lily leaves, where the female may submerge her abdomen to deposit eggs in semicircular rows on the underside of the leaf; a process that can take up to 30 minutes.

Distribution

Eastern U.S. from Maryland south to Florida and west to Texas.