Riffle Darner
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Oplonaeschna armata
Hagen, 1861
Order Odonata
Suborder Anisoptera
Superfamily Aeshnoidea
Family Aeshnidae
Genus Oplonaeschna
Species armata (Hagen, 1861) [Aeschna]
Identification
Where Riffle Darner is found it can be rather common. The male's eyes are blue. The thorax is brown with two lateral thoracic stripes that are blue above fading to yellow below. The anterior lateral thoracic stripe is narrowed at its upper 1/3 to form two separated stripes. The abdomen in the male has small blue spots on the anterior segments and yellow spots on the posterior s
egments, 5-10. The cerci in the male are wedge-shaped and those of the female are as long as segments 9-10, but break off after oviposition. Females may have blue, green or yellow abdominal spots. Eyes of blue-form females are blue-green and yellow-form females have brownish-yellow eyes.
Size
Total length: 67-74 mm; abdomen: 50-57 mm; hindwing: 47-54 mm.
Similar Species
Some mosaic darners (Aeshna
) are similar, but all have a complete anterior lateral thoracic stripe and larger pale spots on the abdomen. The radial planate is unforked in Riffle Darner and forked in mosaic darners.
Habitat
Rocky mountainous streams in hardwood or pine forests subject to periodic flooding.
Discussion
Males patrol most frequently in the morning, but will do so all day. Riffle Darners feed around the lower portions of trees in open forests. One study found adult emergence and flying season were related to annual air and water temperatures. Adults fly for about a month.
Distribution
Southwestern U.S., Arizona, New Mexico and Utah; also Chihuahua, Mexico south to Guatemala.
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