Comal Springs Dryopid Beetle

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Comal Springs Dryopid Beetle

Stygoparnus comalensis

ListedDecember 12, 1997
DescriptionWeakly pigmented, translucent, thin-skinned, subterranean aquatic beetle with vestigial eyes.
HabitatAir-filled voids inside spring orifices.
FoodLikely a predator of other invertebrates
ReproductionHas a complex life cycle of eggs, larvae, and adult.
ThreatsDecrease in water quantity and quality; groundwater pollution.


The Comal Springs dryopid beetle, Stygoparnus comalensis, a recently discovered species, was first collected in 1987 and described as a new genus and species in 1992. This species is the first subterranean aquatic member of the beetle family Dryopidae to be discovered.

Adult Comal Springs dryopid beetles are about 0.12 in (3 mm) long. They are weakly pigmented, translucent, thin-skinned, and have vestigial eyes. Most of the specimens have been taken from drift nets or from inside the spring orifices, with collections taking place from April through August.


The Comal Springs dryopid beetle is a subterranean, blind, flightless, aquatic insect. Its food is unknown, but it is probably a predator of other aquatic invertebrates.


Although the larvae of the Comal Springs dryopid beetle have been collected in drift nets positioned over the spring openings, they are presumed to be associated with air-filled voids inside the spring orifices since all other known dryopid beetle larvae are terrestrial. Unlike Peck's cave amphipod, the Comal Springs dryopid beetle does not swim, and it may have a smaller range within the aquifer.


Collection records for the Comal Springs dryopid beetle are primarily from spring run 2 at Comal Springs, but they have also been collected from runs 3 and 4 at Comal and from Fern Bank Springs about 20 miles to the northeast in Hays County.


The primary threat to the Comal Springs dryopid beetle is a decrease in water quantity and quality as a result of water withdrawal throughout the San Antonio segment of the Edwards Aquifer. Ground-water pollution from human activities also threatens to seriously degrade the water quality of its habitat. This species is especially vulnerable to cessation of spring flow.

Conservation and Recovery

The Comal Springs dryopid beetle is only known from Comal Springs and Fern Bank Springs. The rare beetle will only survive if its critical habitat at these springs is protected, and the essential hydro-logical and water-quality characteristics are conserved. The primary threat is associated with the withdrawal of water from the San Antonio segment of the Edwards Aquifer, so it is crucial that this hydrological use is limited to an intensity that does not degrade the critical habitat. The acceptable rate of water use by humans will have to be determined, and will have to account for the effects of periodic drought on groundwater recharge. It will also be necessary to control the risks of local spills of pesticides, hydrocarbon fuels, fertilizers, and other chemicals, any of which could seriously degrade groundwater and damage habitat. The populations of the Comal Springs dryopid beetle will have to be monitored, and research undertaken into its basic biology and habitat needs.


U. S. Fish and Wildlife Service
Regional Office, Division of Endangered Species
P.O. Box 1306
Albuquerque, New Mexico 87103-1306
Telephone: (505) 248-6911
Fax: (505) 248-6915

U. S. Fish and Wildlife Service
Ecological Services Field Office
10711 Burnet Road, Suite 200
Austin, Texas, 78758
Telephone: (512) 490-0057
Fax: (512) 490-0974


U. S. Fish and Wildlife Service. 18 December 1997. "Endangered and Threatened Wildlife and Plants: Final Rule To List Three Aquatic Invertebrates in Comal and Hays Counties, TX, as Endangered." Federal Register 62 (243):66295-66304.