[Photo: Texas Parks and Wildlife]

Comal Springs Dryopid Beetle
Stygoparnus comalensis

Description: The Comal Springs dryopid beetle is an aquatic subterranean species of the Dryopidae family (long-toed water beetles). Adaptations to its subterranean habitat are evident by its translucent exoskeleton and lack of eyes. This beetle is 0.11-0.15 inches (3-4 mm) long and reddish-brown in color.

Life History: This beetle requires atmospheric oxygen for respiration. Hairs found on the beetle's underside are unwettable and can trap air which the beetle uses to breathe as it swims. Not much is known about the feeding or mating habits of this species; however, they are thought to feed on detritus scraped from rocks.

Habitat: The larvae of the Comal Springs dryopid beetle are terrestrial and live inside air pockets on the soil and debris lining the ceiling of the underground spring orifices. The adults are fully aquatic and live in the spring openings and underground streams of the Edwards Aquifer.

Distribution: Stygoparnus comalensis is found in Comal Springs (Comal County) and Fern Bank Springs (Hays County), in the Edwards Aquifer, Central Texas.

The map below depicts the critical habitat for this species, as designated by the US Fish and Wildlife Service pursuant to the Endangered Species Act.

NOTE: No warranty is given, expressed or implied, as to the accuracy, reliability, or completeness of these data. Data do no represent a legal description of the critical habitat boundary; refer to the textual description in the appropriate final rule for this species as published in the Federal Register.

Comal Springs Dryopid Beetle (Stygoparnus comalensis) Federally Designated Critical Habitat [Figure: Houston Advanced Research Center using US FWS data]

Status: The Comal Springs dryopid beetle is a state and federally listed (1997) endangered species. Water quality in the aquifer is important to the Comal Springs dryopid beetle because of its unique method of respiration. The beetle requires high levels of dissolved oxygen (DO) to breathe and water quality impairments could lower the DO levels to the point of damaging this population. Additionally, due to the fact that this beetle's larvae are terrestrial and adults are aquatic, physical disruption or separation of these habitats could damage the population. Water quantity fluctuation is not as detrimental to this species because it can retreat into the aquifer during low flow periods. At flows of less than 40 cubic feet per second (cfs) damage to this population may occur; and at flows of 20 cfs or less there is a possible legitimate risk to this population.

Resources:

Edwards Aquifer Authority, Draft Edwards Aquifer Habitat Conservation Plan

Texas A&M, Status of the Comal Springs Dryopid Beetle

Texas Parks and Wildlife, Endangered Species of the Edwards Aquifer

US Fish and Wildlife Service, Critical Habitat Final Rule

US Fish and Wildlife Service, Endangered Species Listing