Identification
In flight males appear mostly dark gray with a bold white spot on the upper side of S7 and a pale face. Eyes can be greenish, bluish or pale gray. The abdomen is slender and obviously clubbed from S7-S9.
There are pale whitish or greenish stripes on a bluish-gray thorax. There are two broadly confluent stripes middorsally on the thorax for 2/3 to 3/4 of its length. The broad humeral stripe is brown. Two additional lateal stripes are pale. The wings are sometimes tinged with amber in females have a dark basal spot that is more prominent in the hindwing. The legs are brown becoming darker distally. The abdomen is largely black with pale basal segments. It is slender basally, then slightly expanded at segments 7-9 in males. There are paired bluish-gray spots dorsally on segments 3-6, but these quickly become obscured with age. Segment 7 bears a pair of large pale dorsal spots that are never obscured.
Size: Total length: 52-64 mm; abdomen: 34-46 mm; hindwing: 32-44 mm.
Similar Species: The clubbed abdomen, color and markings of this species may lead to its misidentifications as a clubtail (Gomphidae), but the eyes are in contact on top of the head. Clubskimmers hang vertically rather than perching horizontally like many clubtails. Tropical dashers (Micrathyria) are much smaller and behave differently.
Masked Clubskimmer (Brechmorhoga pertinax) occurs in SE Arizona and differs in having a dark black forehead.
Slender Clubskimmer (Brechmorhoga praecox) is smaller than our other two clubskimmers with a less prominent club. Currently only known from the Lower Rio Grande Valley of Texas, within the U.S.
Habitat: Flowing sand and cobble streams, rivers, canals and drainage ditches in arid, open areas. In southern California found along long open sunny stretches of flowing streams, rivers, washes and canals.
Natural History: Males of this species typically have small territories that they patrol low over the water, normally less than 1 m but sometimes up to tree height. They often perch in the shade and can be elusive and difficult to approach. This species has been described as the most graceful on the wing of any North American odonate. Flight is steady, smooth and graceful. During the heat of the day this species will patrol a section of stream, remaining on the wing for extended periods.
This species hangs vertically, never perching horizontally. Females lay eggs by making short straight or figure eight runs low over the water and dipping eggs at the surface. Adults are active all day, but may retreat to shaded areas of the stream in the heat of the day. They are often abundant at dusk in clearings near streams where they feed on emerging mayflies and caddisflies.
Distribution: Southwestern U.S. and Great Plains; Mexico. This species is widespread throughout the southwest from California to Texas and Oklahoma and occurs rarely up the great plains to the Dakotas.
Reference: David Bell, adapted from https://odonatacentral.org/index.php/FieldGuideAction.get/id/46864
Reviewed by John C. Abbott
