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Arrowhead Spiketail



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Cordulegaster obliqua

Say, 1839


Order Odonata
Suborder Anisoptera
Superfamily Cordulegastroidea
Family Cordulegastridae
Genus Cordulegaster
Species obliqua (Say, 1839) [Aeschna]


Identification

Like Twin-spotted Spiketail (C. maculata ) this species is restricted to the eastern limits of the region. The eyes are aqua-blue. There are two broad pale yellow stripes laterally on the thorax. The wings are clear and rarely become smoky. The abdomen is dark red-brown with yellow spear-shaped marks on segments 2-7. Two forms, both of which occur in the region, are recognized. The northern form (C. obliqua obliqua (Say)), is found in Texas and is generally smaller, 72-80 mm. The forewing triangle is usually comprised of 2-cells and the anal triangle of the male is 3-celled. The southern form (C. obliqua fasciata Rambur ) is found in Arkansas and Louisiana and is generally larger, 82-88 mm. The forewing triangle is generally 3-celled and the anal triangle in males is comprised of 4-cells.

Size

Total length: 72-88 mm; abdomen: 48- 72 mm; hindwing: 41-60.

Similar Species

In addition to a later emergence period, Arrowhead Spiketail can be separated from Twin-spotted Spiketail by a row of spear-shaped dorsal pale yellow markings on the abdomen. Arrowhead Spiketail is also darker than Twin-spotted Spiketail, often appearing nearly black. See also the discussion of similar species for Twin-Spotted Spiketail.

Habitat

Small, rapidly flowing spring-fed forest streams and seepages with sandy or muck bottoms.

Discussion

This species emerges later and has a longer flight period than Twin-spotted Spiketail, but is less likely to be encountered. It is uncommon and elusive throughout its range. Little has been published about its behavior, but as far as is known, it is similar to Twin-Spotted Spiketail. It flys up and over tree tops when disturbed.

Distribution

Eastern U.S. and Canada.