Major Group: Insecta
Order: Coleoptera
Family: Psephenidae
Genus: Sclerocyphon
This family is represented in Australia by a single genus, Sclerocyphon.
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Descriptive Features:
Adults
antennae 11-segmented without distinct club
posterior edge of pronotum distinctly crenulate
ventral portion of the notum, (hypomeron) on each side joined directly to the sternum by notosternal
suture
pleuron reduced and concealed
prosternum in front of coxae much longer than intercoxal process
body very short and broad, less than 1.5 times as long as wide
abdomen with at least 3 connate ventrites
elytra exposing less than 2 complete abdominal tergites
mesocoxal cavities narrowly separated
intercoxal process on ventrite 1 narrowly rounded
tarsi simple
size:
Larvae
head completely concealed from above by prothorax
antennal length >˝ head width
labrum separated from head capsule by complete suture
mandibular mola absent
body broadly ovate, strongly flattened, disc-like
legs 5-segmented, including claws
abdominal apex with ventrally hinged operculum, concealing 3 extrusible tufts of fine, slender gills
size: 6.4 - 9.0mm
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Sclerocyphon maculatus larva |
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Sclerocyphon adult |
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Taxonomic Checklist: Species
Sclerocyphon aquaticus Lea
Sclerocyphon aquilonius Davis
Sclerocyphon basicollis Lea
Sclerocyphon collaris Fabricius
Sclerocyphon fuscus Bertrand & Watts
Sclerocyphon lacustris Davis
Sclerocyphon maculatus Balckburn
Sclerocyphon minimus Davis
Sclerocyphon nitidus Davis
Sclerocyphon secretus Smith
Sclerocyphon serratus Lea
Sclerocyphon striatus Lea
Sclerocyphon zwicki Davis
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Distribution: E Qld, E NSW, Vic, Tas
Sensitivity Rating: SIGNAL grade 6
Functional Feeding Group: scrapers (larvae); terrestrial adults
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Mt Wills Creek near Granite Flat, Vic |
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Ecology: Instream habitat: Commonly known as ‘water pennies’, Sclerocyphon larvae cling to rocks in strongly flowing or turbulent sections of streams and rivers but they can also survive in well-oxygenated stretches of stagnant water. The larvae are usually absent from loosely packed substrates, sandy substrates and highly enriched or silted streams. Adults are terrestrial and cryptic, usually remaining hidden in leaf and twig litter, high-water leaf packs or debris and riparian vegetation on stream banks.
Feeding ecology: Larvae are grazers and scrapers feeding on the biofilm associated with stream rocks and wood. No information is available on the feeding habits of adults.
Habit: The larvae avoid daylight by clinging to the underside of stones in streams. In dim light and at night they crawl to the upper surfaces to graze. Larvae breathe dissolved oxygen in the water through a tuft of anal gills and they can breathe atmospheric oxygen when out of water. Adults have been observed flying above streams on hot days.
Life history: Larval development seems to incorporate 5-6 instars, with little development over winter months. Temperature seems to be the main factor influencing larval growth and overall duration of the lifecycle. In Tasmania, the life cycle completes in 24 months whereas in Queensland the life cycle completes in only 12 months. Final instar larvae leave the water in spring and remain hidden for several weeks under rocks, logs or litter on the bank before pupating. There is a pre-pupal phase and pupation occurs within the last larval skin. Pupae often cluster in one spot with the pupal stage lasting from two to three weeks. Adults live up to three weeks within terrestrial litter where they mate. Females return to the water to lay their eggs, which are virtually invisible to the naked eye, in a single layer under submerged rocks. The larval stage is present in streams and rivers throughout the year (22 months from a 24 month cycle) while the adult and pupal stages are short lived for a few weeks in spring and summer. The egg phase is also very short.
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Information Sources: Davis 1998, Davis 1986, Lawrence & Britton 1991, Calder 1999c, Williams 1980, Gooderham & Tsyrlin 2002
Key to Species: Davis 1998 (larvae)
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