Hydora Anon. [Broun], 1882

Barr, Cheryl B. & Shepard, William D., 2021, A review of the Larainae of Australia with description of seven new species and the new genus Australara (Coleoptera, Byrrhoidea, Elmidae), ZooKeys 1073, pp. 55-117 : 55

Genus Hydora Anon. [Broun], 1882

Type species.

Pachycephala picea Broun, 1881.

Diagnosis.

Body elongate, sides subparallel; antennae loosely clavate; eyes large, prominent; pronotum with two basal sublateral carinae; prosternum not extended anteriorly beneath head; elytra striate-punctate, punctation sometimes reduced (New Zealand species), each elytron with one accessory basal stria between striae 1 and 2, elytral apices narrowly rounded; tarsi each with tarsomere 5 subequal to or shorter than tarsomeres 1-4 combined; abdominal ventrites 1 and 2 combined shorter than ventrites 3-5 combined.

Distribution.

The genus Hydora has an interesting geographic distribution, with ten recognized species occurring in New Zealand (7), Australia (1), and Argentina and Chile (2) ( Spangler and Brown 1981; Lambert et al. 2014). There are many currently undescribed species in New Zealand and one in Chile (R. Leschen, V. Sýkora, in litt.).

Habitat and behavior.

There is no information available pertaining to the habitat and behavior of Hydora in Australia, except for the fact that at least half of the known specimens were collected at lights. In New Zealand, larvae and adult Hydora are common on the bottom substrate, or on vegetation, including bryophytes, at the margins of moderate to fast flowing streams ( Lambert et al. 2014). Adults can sometimes be found running around on the emergent parts of boulders and have been observed in mass swarms above the water surface ( Lambert et al. 2014).

Comments.

In this genus the prosternal process may or may not have a median longitudinal carina, depending on the species. Some New Zealand species do, and some do not ( Broun 1914; Lambert et al. 2014). No carinae were mentioned in the descriptions of the prosternal processes of the two species from Austral South America, Hydora annectens Spangler & Brown and H. lenta Spangler & Brown ( Spangler and Brown 1981), and upon examining specimens of those species, we found none. The description of H. laticeps from Australia stated that the process is without a carina ( Carter and Zeck 1932), but this is debatable. The prosternal process is discussed in the Comments section of the species treatment. The larva was keyed and illustrated at the generic level in Glaister (1999) based on New Zealand specimens.