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 Major Groups | Insecta (insects) | Coleoptera (beetles) | Hydraenidae


Major Group: Insecta
Order: Coleoptera
Family: Hydraenidae

Descriptive Features:

  • antennae 9-segmented with 5-segmented club
  • prothorax without notopleural sutures, ventral portion of the notum, (hypomeron) on each side joined directly to the sternum by notosternal suture and pleuron reduced and concealed
  • abdomen with more than 3 ventrites
  • ventrite 1 not divided by hind coxae
  • elytra exposing less than 2 complete abdominal tergites
  • size: 0.8 - 2.5mm
  • maxillary palp 2- or 3-segmented
  • antennae 3-segmented; maxillary palps 3-segmented
  • labrum separated from head capsule by complete suture
  • mandibular mola present
  • basal portion of labium completely free or basally connate with maxillae
  • bases of frontal arms contiguous
  • epicranial stem present
  • tergum 9 with articulated urogomphi
  • legs present
  •  size: up to 2.5mm

    Hydraenidae larva


    Hydraena ypsilon adult

    Taxonomic Checklist: Genera
    8 species
    Gymnochthebius 33 species
    Hydraena 85 species
    Limnebius acupunctus Perkins
    Octhebius queenslandicus Hansen
    Tympanogaster 84 species*
    * possibly only the subgenus Tympanogaster (sensu stricto) 38 species are semi-aquatic

    Distribution: Australia wide

    Sensitivity Rating: SIGNAL grade 3

    Functional Feeding Group: scrapers (adults), predators (larvae)


    Billabong Creek at Wanganella, NSW

    Ecology: Hydraenidae species are mostly aquatic, but some species are terrestrial throughout the life cycle.
    Instream habitat: Hydraenid beetles live in a variety of riparian, littoral and aquatic habitats, including inland salt lakes. As a family, they are often abundant at the edges of gravely rivers and streams. Most Hydraena species also prefer shade with some leaf litter or aquatic plants. A few species appear to live only in ponds and at least one species, Hydraena hamifers, is found primarily in humicolous microhabitats. Meropathus species inhabit moss in the spray zone of cascades and waterfalls. Adults and larvae of Tympanogaster live in the vegetation on rocks in mountain streams where they are not always covered by water but are kept wet by splashes. Ochthebius species appear to live in algal crusts of mud and sand in marginal areas of flowing waters and standing fresh or saline waters.
    Feeding ecology: Adults of Australian species are mainly herbivores feeding on algae. Larvae are thought to be scavengers. Northern hemisphere studies indicate that adults and larvae of some species may be detritivores
    Habit: Adults hydraenid beetles crawl upside down just under the water surface with an air bubble on the ventral side of the abdomen. Hydraena beetles crawl on vegetation and merely float to the surface if they become dislodged.
    Life history: In the northern hemisphere, hydraenid beetles lay eggs on wood and stones just beneath the waterline. Early instar larvae leave the water but live near to it.


    Information Sources: Watts 2002, Perkins 2004b, 2006, 2007a, 2007b, Lawrence & Britton 1991, Mathews 1982, Williams 1980, Gooderham & Tsyrlin 2002, Ribera & Vogler 2000
    Key to Genera: Watts 2002 (adults, partial)
    Key to Species: Perkins 2004a (Gymnanthelius adults)
    Perkins 2005 (Gymnochthebius adults)
    Perkins 2006 (Tympanogaster adults)
    Perkins 2007a (Hydraena adults - monograph not key)