Insects and their Allies  

Megaloptera: dobsonflies and alderflies

This is a very small order of Australian insects commonly known as alderflies and dobsonflies. They are medium to large sized insects with a wingspan ranging from 20 to 100 millimetres. Alderflies and dobsonflies can be recognised by the following features:

Archichauliodes species
Archichauliodes species (CORYDALIDAE)

  • Long, soft, flexible bodies, usually dark coloured

  • 2 pairs of membranous wings of similar size, often bearing dark patches.

  • At rest the wings are held roof-like over the body

  • Mandibulate mouthparts

  • Long filiform antennae which taper towards the end

CORYDALIDAE is a widespread family of dobsonflies and well represented in Australia. Archichauliodes species are inhabitants of cold-water streams and can be found from southern Australia to north Queensland. Adults of this species can usually be recognised as they have 4 or 5 large spots on their hind wings in addition to many smaller spots towards the edges of the wing.

The larvae of alderflies and dobsonflies are aquatic, appear caterpillar-like and possess gills along the sides of their abdomens.

Archichauliodes species
Archichauliodes species (CORYDALIDAE)

Members of Megaloptera are sometimes confused with lacewings (Neuroptera) and stoneflies (Plecoptera). Alderflies and dobsonflies can be distinguished from lacewings by the absence of terminal branching wing veins and from the later as stoneflies possess abdominal cerci and hind wings that are larger and broader than their forewings.

Life Cycle
All species have aquatic larvae and mating occurs on the vegetation close to freshwater streams. Female alderflies and dobsonflies may lay up to 3000 eggs on rocks or debris close to the stream but not in the water. When the larvae hatch they enter the water and live a permanently aquatic life until they are ready to pupate. At this stage the larvae move out of the water into the adjacent leaf litter or soil where they pupate for several weeks. The complete life cycle may take only one year in warmer areas or up to 5 in colder climates.

The adults are most active at dusk and during the night but do not appear to feed. The larvae however are active predators of other aquatic invertebrates and have strong mandibles with which to grasp their prey.

Alderflies and dobsonflies are not strong fliers and are therefore found close by freshwater streams due to their aquatic larvae. The adults can often be found on the vegetation along side streams and are sometimes attracted to lights at night. The larvae can be found on the bottom of clear, cool freshwater streams. Megalopteran species are more common along the eastern side of Australia from Cape York to Tasmania with only one species occurring in the south west of Western Australia.