![]() Forewings are modified into hardened covering (elytra), which protects the top of abdomen and the second pair of membranous wings. These adaptations make dytiscids exceptionally efficient swimmers.Īs like in terrestrial beetles, all the body is well armored. Other four legs are trucked into grooves along the sides to preserve streamlined body shape. On the return stroke they bend in to reduce water resistance. ![]() The hairy fringes spread out on the power stroke, which increase the surface area. Hind legs are equipped with dense rows of swimming hairs. In general, the body is more streamlined in shape and flattened (compared to terrestrial beetles). Adults and larvae rely on atmospheric oxygen, therefore can be found even in habitats with low level of dissolved oxygen.ĭiving beetles may look very similar to their terrestrial relatives, but dytiscids have developed some modifications, which enable them to be so successful and diverse. The greatest diversity is reached in still waters such as ponds, wetlands, billabongs, or in slow flowing waters with lot of vegetation. Beetles entered aquatic environment after millions of years evolving on land, yet they can be found in almost any freshwater habitat. One third of all insects belongs to this single order.Įven though most beetles are terrestrial, many of them have colonized freshwater habitats and spend at least one of their life stages as aquatic. ![]() In diversity, Coleoptera is the largest order of insects (containing more than 400 000 described species) and one of the largest groups of animals on Earth. Most species produce one generation per year. Their life cycle includes four stages – egg, larva, pupa and adult. Size of the adult diving beetles varies from 2 mm to 45 mm.ĭiving beetles undergo complete metamorphosis. They are common in temporary pools, wetlands, marshes, ponds and slow sections of flowing waters. It is not known whether this species historically ranged in other springs that are now dry almost all the time, such as San Pedro Springs and San Antonio Springs.Diving beetles can be found in almost any freshwater habitat. POPULATION TREND: Comal Springs riffle beetles have been collected from spring runs 1, 2 and 3 at Comal Springs and a single specimen was taken from San Marcos Springs. Exotic species negatively affect the beetle through competition for food, displacement or destruction of aquatic vegetation, and general habitat degradation. Other threats associated with increased urbanization include increased flooding and erosion, pollution, siltation, and storm-water runoff. THREATS: The main threat to the survival of the Comal Springs riffle 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. ![]() All life stages except that of the egg make take place throughout the year.įEEDING: Larval and adult riffle beetles both feed on microorganisms and debris scraped from the substrate. LIFE CYCLE: All beetles undergo complete metamorphosis with life cycles consisting of an egg, larva with multiple instars, pupa, and adult. MIGRATION: This beetle has not been known to migrate.īREEDING: Riffle beetles typically deposit eggs on the underside of submerged rocks and debris. RANGE: Comal Springs riffle beetles are known from three spring runs at Comal Springs in Landa Park, as well as San Marcos Springs, 20 miles to the northeast. The water in occupied habitat is usually about one to four inches deep, although the beetle may also occur in slightly deeper areas within the spring runs. HABITAT: The Comal Springs riffle beetle occurs in gravel substrate and shallow riffles in spring runs. The larva has an elongate, tubular body and can be up to 10 millimeters in length. It is reddish brown in color and has short hind wings and a narrow body. COMAL SPRINGS RIFFLE BEETLE } Heterelmis comalensisĭESCRIPTION: The Comal Springs riffle beetle is an aquatic, surface-dwelling species of about two millimeters in length, with females slightly larger than males.
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