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NATURAL HISTORY

COMAL SPRINGS DRYOPID BEETLE } Stygoparnus comalensis
FAMILY: Dryopidae

DESCRIPTION: The adult Comal Springs dryopid beetle is about three millimeters long with elongate legs, an oblong, slender body, and a thin, translucent, reddish-brown cuticle. Larvae are elongate, cylindrically shaped, and yellowish brown in color. Neither the adult nor the immature stages have functional eyes.

HABITAT: Adult dryopid beetles are fully aquatic and live primarily in the flowing, uncontaminated waters of Comal, Texas, and Fern Bank springs and the associated Edwards Aquifer in Texas. Larvae are presumed to reside in air-filled voids inside spring orifices. The exact depth and subterranean extent of the species is not precisely known; however, it is thought to be confined to small areas surrounding the spring openings and not distributed throughout the aquifer. Trees and shrubs with roots that travel underground are thought to be part of this beetle’s habitat.

RANGE: The Comal Springs dryopid beetle is primarily known from three spring runs at Comal Springs, but it has also been collected from Fern Bank Springs about 320 miles to the northeast in Hays County.

MIGRATION: The Comal Springs dryopid beetle has not been known to migrate.

BREEDING: Little information is available about the reproduction of the Comal Springs dryopid beetle; however, it is known to breed in subterranean habitat.

LIFE CYCLE: All beetles undergo complete metamorphosis with life cycles consisting of an egg, larva with multiple instars, pupa, and adult. All life stages except that of the egg make take place throughout the year.

FEEDING: The exact feeding habits of this beetle are unknown, but all other dryopid beetles feed on decomposing organic matter and possibly plants. Captive adults of this species have been seen grazing on the surface of rocks.

THREATS: The main threat to the survival of the Comal Springs dryopid beetle is decreased spring flow due to increased use of groundwater resources throughout the Edwards Aquifer region, which may prove fatal to the species when coupled with periodic drought. Other threats associated with increased urbanization include increased flooding and erosion, pollution, siltation, and storm-water runoff. Exotic species negatively affect the beetle through competition for food, displacement or destruction of aquatic vegetation, and general habitat degradation.

POPULATION TREND: Collection records for the Comal Springs dryopid beetle are primarily from spring run 2 at Comal Springs, but the species has also been collected from runs 3 and 4 at Comal Springs as well as from Fern Bank Springs.

Photo by Joe N. Fries, USFWS