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Spot-tailed Dasher

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Micrathyria aequalis

Hagen, 1861

Order Odonata
Suborder Anisoptera
Superfamily Libelluloidea
Family Libellulidae
Genus Micrathyria
Species aequalis (Hagen, 1861) [Dythemis]


This small species occurs in the lower Rio Grande Valley of southernmost Texas. Its face is nearly white with grey eyes that become brilliant gree n and the top of head is metallic green in mature males. The thorax is pale yellowish-green in females and young males. The front of the thorax has a pair of yellowish stripes and each side has 3 diffuse brown stripes along lateral sutures, confluent below to form a WII pattern. The wings are clear and the legs are black. The slender abdomen is brown with a pair of interrupted pale stripes dorsally, ending on segment 7 or 8. Older males become heavily pruinose, obscuring the thoracic and abdominal pattern with gray. Females usually retain this pattern pattern, but colors may be dull and wingtips darken.


Total length: 26-34 mm; abdomen: 15-24 mm; hindwing: 20-26 mm.

Similar Species

Blue Dasher (Pachydiplax longipennis), Three-striped Dasher (M. didyma ) and Thornbush Dasher (M. hagenii ) are all similar but all have 3 distinct straight black stripes or a IYI pattern laterally on the thorax. Females of Seaside Dragonlet (Erythrodiplax berenice ) are easily distinguished by the prominent ventrally projecting ovipositor. Swift (Dythemis velox ) and Black (D. nigrescens ) Setwings are larger, have dark wingtips and a different lateral thoracic pattern. Pale-faced Clubskimmer (Brechmorhoga mendax ) is much larger.


Permanent and temporary ponds, sloughs and lakes.


This species barely gets into the southern tip of Texas where it can be locally common. Individuals may fly furiously along the edges of their pond habitats. Males will perch at varying heights up to 2 m over the water on twigs and branches, usually exposed to sunlight. Females tend to remain farther back from water when not mating or laying eggs. On warmer days both sexes will adopt a typical obelisk position. Females lay eggs alone, but are often interrupted by males. Females land on floating leaves below which they invert the end of the abdomen to deposit eggs on the underside. An estimated 2,000 eggs have been documented in a square inch area though these are probably not all from the same female.


Southern Florida and Texas, West Indies and Central America south to Ecuador.