What Bug Is That? The guide to Australian insect families.

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Baetids are extremely widespread and abundant in Australia. Baetis (4 spp.), Cloeon (5 spp.), Centroptilum (2 spp.) and Pseudocloeon (1 sp.) are cosmopolitan while Bungona (1 sp.), is endemic. The family has received comparatively little study in Australia and undoubtedly there are undescribed species.


Nymphs are small (less than 1 cm long), slender and streamlined, with plate-like gills. They differ from nymphs of siphlonurids by their smaller size and longer antennae, and in the structure of the labrum. Adults have transparent wings with reduced venation. Bungona , Cloeon and Pseudocloeon all lack hind wings.
In males the compound eyes are divided completely with the dorsal part developed into a large, turbinate structure. The eyes of females are small and comparatively simple. The penes of the male are membranous and extrudable.


Baetis occur only in permanent, flowing water and are most common in the clear water of cold streams. The genus is widespread in Tas., the eastern mainland (including S.A.) and the south-west of W.A. (Bunn et al. 1986). Nymphs appear to feed mostly by scraping algae and fine particulate detritus from solid surfaces (Chessman 1986). One species of Baetis in a Victorian high mountain stream is univoltine with a summer emergence period (November-March) (Duncan 1972). Baetis soror is univoltine in one S.A. stream and bivoltine in another; both populations have multiple cohorts, with emergence over at least 9 months of the year (Suter 1980; Suter and Bishop 1980).
Centroptilum and Baetis occur in similar habitats and sometimes together, but generally Centroptilum is absent from north-eastern Australia. Nymphs are generally larger than those of Baetis and have greatly elongated tarsal claws but apparently they feed in a similar fashion.
Cloeon is widespread in eastern Australia from Tas. to the tropics. Nymphs are most common in standing waters such as billabongs and farm dams and are also found in slowly flowing reaches of rivers. Nymphs of at least one species feed mostly on filamentous algae (Chessman 1986). In a seasonal creek in the N.T., nymphs of Cloeon fluviatile develop rapidly (about 4 weeks) and eggs can resist desiccation during dry months (Marchant 1982).
Bungona narilla was collected from a small coastal stream near Sydney but nothing more is known of its biology. Pseudocloeon are very small and occur in the mountain streams of coastal Qld and N.S.W. (Riek 1970).

  • Edmunds sp. nymph

  • Centroptilum sp. nymph

  • Offadens sp. nymph

  • Cloeon sp.