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

Megaloptera (dobsonflies, alderflies)

Major Group: Insecta
Order: Megaloptera

Descriptive Features:

  • wings absent
  • mouthparts biting, mandible and maxilla developed for grasping and chewing
  • abdomen with or without 1 caudal filament
  • 3 pairs of jointed legs present on thorax
  • abdominal segments 3-6 without prolegs
  • abdominal segments 1-7 or 1-8 each with a pair of strong, long lateral processes
  • abdomen ending in EITHER a long terminal process ORa single pair of hooks on prolegs
  • total length: up to 50mm
  • Taxonomic Checklist:



    Distribution: Vic, S WA, NE Qld, ACT, E NSW, E Tas

    Sensitivity Rating: SIGNAL grade 8

    Functional Feeding Group: predators

    Ecology: Instream habitat: Megaloptera species occur in spring seepages, streams, rivers, swamps, ponds and lakes. They are usually associated with clear, cold still or flowing waters, but some records are from swamps and silty or muddy sections of slowly flowing streams although they are sensitive to human disturbances. 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 1988, Williams 1980
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