Ecology: Instream habitat: Most hydrophild beetles occur in slow moving streams or shallow, still waters such as ponds, dams, bore drains and stock water troughs. However species of Laccobius, Berosus and Sternolophus also occur in fast flowing streams.
Feeding ecology: Known as ‘water-scavenger beetles’, adults are scavengers, feeding on plants or decaying plant matter, and larvae are predators, feeding on snails, worms, small crustaceans and insect larvae. An exception is Helochares which is herbivorous.
Habit: Most hydrophilid beetles are poor swimmers except for Laccobius, Berosus and Sternolophus.
Life history: Hydrophilid adults are most abundant during spring and summer. Larvae and pupae occur in large numbers in late sprint and early summer (October, November and December), with numbers declining rapidly as summer progresses (early January). Hydrophilidae species over winter mostly as adults, although larvae may still be collected throughout winter.
Males use calling signals under water to find mates. Females of some genera carry their eggs beneath their abdomen but most females enclose their eggs within a densely woven silk cocoon with one end drawn out into an elongate mast that helps with respiration. Cocoons are usually attached to emergent vegetation just above the water level or in riparian areas adjacent to water. Pupation occurs upon land.
In the laboratory, duration of the Helochares tristis life cycle was 33-134 days; egg (5-10 days), 1st Instar larva (1-14 days), 2nd instar (5-21 days), 3rd instar (5-7 days). The interval between contraction of the pupa and ecdysis was one hour. Duration of the Helochares nitescens lifecycle was 24-33 days; eggs (5-7 days), 3rd instar larva (after 21 days), pupa (3-4 days). Duration of the Enochrus maculiceps life-cycle was 31-54 days; eggs (5-7 days), 1st instar larva (1-14 days), 2nd instar larva (7-14 days), 3rd instar larva (14-35 days), pupa (3-4 days). Single females produced 5-6 egg bags per season.
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Information Sources: Watts 2002, Calder & Wells 2004, Mathews 1980, Williams 1980, Gooderham &Tsyrlin 2002, Hebauer 2003, Anderson 1976
Key to Genera: Watts 2002 (adults and larvae, incomplete)
Hebauer 2003 (adults, partial, worldwide)
Key to Species: Komarek 2007 (Anacaena (Paracaena) adults)
Gentili 2006 (Notohydrus adults)
Gentili 2000 (Paracymus adults)
Hebauer & Hendrich 1999 (Helochares adults, incomplete)
Watts 1998a (Enochrus adults)
Watts 1998b (Amphiops, Allocotocerus adults)
Watts 1990 (Hydrobiomorpha adults)
Watts 1989 (Sternolophus adults)
Watts 1988a (Hydrophilus adults)
Watts 1987 (Berosus adults)
Gentili 1980 (Laccobius, Notohydrus adults)
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