Riffle beetle larvae7/25/2023 ![]() The genus Ancyronyx was established in 1847 by the German entomologist Wilhelm Ferdinand Erichson based on the type species Macronychus variegatus first described in 1824 by the German coleopterologist Ernst Friedrich Germar. The genus contains twenty-one species, eleven of which are endemic to the Philippines. They feed on algae and decaying wood tissue. Both the adults and the larvae are found underwater in the shallow riffles of streams and rivers, clinging to rocks or submerged wood. They are small beetles with extremely long legs ending in strong claws. "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.Ancyronyx, commonly known as spider water beetles or spider riffle beetles, is a genus of aquatic riffle beetles from North America, South Asia, China, and Southeast Asia. Regional Office, Division of Endangered Species The populations of the Comal Springs riffle beetle will have to be monitored, and research undertaken into its basic biology and habitat needs. ![]() 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 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. 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 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 Comal Springs riffle beetle is only known from Comal Springs and San Marcos Springs. Groundwater pollution from human activities threatens to seriously degrade the water quality of its habitat as well. The primary threat to the Comal Springs riffle beetle is a decrease in water quantity and quality as a result of water withdrawal throughout the San Antonio segment of the Edwards (Balcones Fault Zone) Aquifer. The Comal Springs riffle beetle has been collected from spring runs at Comal Springs in Landa Park and a single specimen was collected from San Marcos Springs 20 mi (32 km) to the northeast. ![]() Populations are reported to reach their greatest densities from February to April. Usual water depth in this occupied habitat is 1-4 in (2.5-10 cm), although the beetle may also occur in slightly deeper areas within the spring runs. It occurs in the gravel substrate and shallow riffles in spring runs. Its food is unknown, but it is probably a predator of other invertebrates. The Comal Springs riffle beetle forages in aquatic gravel, and is flightless. Larvae have been collected with adults in the gravel substrate of the spring headwaters and not on submerged wood as is typical of most Heterelmis species. comalensis are short and almost certainly non-functional, making the species incapable of this mode of dispersal. Some riffle beetle species can fly, but the hind wings of H. The Comal Springs riffle beetle is not a subterranean species. Adult Comal Springs riffle beetles are about 0.12 in (3 mm) long, with females slightly larger than males. glabra, a species that occurs farther to the west in the Big Bend region. It was first collected in 1976 and was described in 1988. The Heterelmis comalensis (Comal Springs riffle beetle) is an aquatic, surface-dwelling species in the family Elmidae known from Comal Springs and San Marcos Springs. Has a complex life cycle of eggs, larvae, pupa, and adult.ĭecrease in water quantity and quality groundwater pollution. Likely a predator of other invertebrates. ![]() ![]() Gravel substrate and shallow riffles in spring runs. Comal Springs Riffle Beetle Heterelmis comalensis Status ![]()
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