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 Major Groups | Insecta (insects) | Megaloptera (alderflies, dobsonflies) | Sialidae


Major Group: Insecta
Order: Megaloptera
Family: Sialidae

Descriptive Features:

  • abdomen with 7 pairs of articulated lateral processes (gills)
  • apical segment of abdomen without prolegs but with terminal filament
  • postlabium markedly shorter than or subequal to gula
  • pedicel much longer than or subequal to flagellar segments of antennae
  • flagellar segments subequal in length
  • Total length:

      Stenosialis sp.

      Taxonomic Checklist: Genera
      Austrosialis Tillyard (2 species)
      Stenosialis Tillyard (2 species)

      Distribution: NE Qld, E NSW, Vic, E Tas

      Sensitivity Rating: SIGNAL grade 5

      Functional Feeding Group: predators


      Mersey River, La Trobe Tas

      Ecology: Instream habitat: Sialid larvae occur in spring seepages, streams, rivers, swamps, ponds and lakes. They are usually associated with clear, cold waters, but some records are from silty or muddy sections of slowly flowing streams. Larvae live under rocks and debris, even in the mud and silt. Adults are found on the stems of riparian vegetation.
      Feeding ecology: Larvae are active predators, feeding on small aquatic invertebrates. Most adults do not feed.
      Life history: Mating takes place in vegetation near water with the males and females communicating by vibration signals. Females lay their eggs in compact masses, of 200 to more than 300, on vegetation or on rocks over-hanging or emerging from water. The eggs are generally placed in positions protected from the sun. Many females aggregate their egg laying such that the total egg mass cover considerable areas and resemble lichens encrusting rock. Eggs hatch in one to four weeks. After hatching, larvae drop into the water and sink to the bottom. Larvae pass through 10-12 instars. Pupation occurs in chambers, usually in riparian soil or litter. The pupal phase lasts only a couple of weeks but larvae may remain for long periods in the pupal cell before actually pupating. Adults are short lived and emerge in late spring to autumn. The life cycle of Megaloptera ranges from one to five years.


      Information Sources: Theischinger 1991, 2000a, Theischinger & Houston 1999, Williams 1980
      Key to Genera: Theischinger 2000a
      Key to Species: none