Ecology: Commonly known as ‘diving beetles’, Dytiscidae species are true aquatic beetles as they live entirely in the water as both adults and larvae.
Instream habitat:At family level, dytiscid beetles live in a variety of lentic and some lotic freshwater habitats. They are most abundant in the littoral zone at the edge of ponds and lakes and are also found in water filled ditches, dams, billabongs, pools in intermittent streams and inland saline lakes. This wide range of habitats includes numerous types of substrata; rock, pebbles, gravel, sand, mud, silt, peat and other organic debris. Of particular interest, at generic level; Antiporus can also be found in acid peat lands where the substratum consists of peat and rotting plant debris; Necterosoma prefer slow flowing, deep streams with a rocky substratum, covered with a thin layer of organic matter; Sternopriscusare often found within vegetation in various parts of water bodies.
Feeding ecology: Both adults and larvae are predators on other aquatic animals, including insects, crustaceans, worms, leeches, molluscs, tadpoles and even small fish. However, the feeding method may differ between adults and larvae of the same species. All adults and some larvae ingest solid and liquid food through a mouth opening. Most larvae have closed mouth openings and so use mandibular channels to inject digestive enzymes into their prey and then suck up the resulting fluids.
Habit: Larvae and adults breathe atmospheric air. The term ‘diving beetle’ comes from the adult behaviour of coming to the water surface to replenish their air supply then returning to swimming well below the surface. Adult dytiscid beetles store oxygen in a bubble beneath the elytra whilst larvae use a siphon located at the tip of the abdomen to draw in air. There are two general forms of larvae; 1) a creeping and burrowing form which are heavier than water and must climb or swim to the surface, 2) buoyant forms which put in effort to stay submerged.
Life history: Female dytiscid beetles are more selective in choosing a mate than males and in some cases have behaviours to resist mating, such as swift and erratic swimming when approached by a male. Males have a variety of methods to achieve mating with some having sucker-shaped setae on their legs which allow them to grab females and prevent them from escaping during mating. After mating, females of many species deposit eggs into slits in stems of aquatic plants, made by an ovipositor. When the first larval instar hatches it is usually attached to an aquatic plant and appears to be independent of surface air, at least initially. The second and third instars need to breathe surface air, which is taken in through paired spiracles at the tip of the abdomen. Pupation takes place in a cell formed by larvae in damp soil, but out of water. At this stage, pupae can drown in a flooding event. New adults return immediately to the water. Most Dytiscidae species seem to have a defined breeding season of two to three months, usually in late winter and spring in southern Australia and during the wet season in northern Australia. During summer, larval stages take three to eight weeks and the pupal stage one to two weeks. Some genera, e.g. Barrethydrus, are winter breeders with a longer life cycle. It is not known whether species, particularly those from alpine and sub-alpine areas, over winter as eggs. It is also possible that other species aestivate over summer during dry periods.
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Information Sources: Lawrence & Britton 1991, Mathews 1980, Watts 1978, 1998c, 2002, Hendrich & Wang 2006, Hendrich 2001, 2003a,b, Watts et al 2007, Balke et al. 2004, Hendrich & Watts 2004, 2007, Watts & Pinder 2000, Bistrom 1996, Watts & Humphreys 2003, Hendrich & Frey 2008, Gooderham & Tsyrlin 2002, CSIRO 2007
Key to Genera: Watts 2002
Key to Species: Watts 1978 (all adults partial)
Watts & Leys 2006 (Hyphydrus adults)
Watts & Humphries 2006, 2004 (Stygobiotic adults inc. Copelatus, Limbodessus, Kintingka, Bidessodes, Nirripirti)
Watts & Leys 2005 (Limbodessus adults)
Alarie & Watts 2005 (Hyphydrus larvae)
Hendrich & Watts 2004 (Sternopriscus adults partial)
Watts 2000 (Tiporus adults)
Balke et al. 2000 (Rhantus adults)
Hendrich 1999 (Hydroglyphus adults)
Hendrich 1997 (Cybister adults)
Watts 1997 (Antiporus adults partial)
Brancucci & Monteith 1996 (Terradessus adults)
Bistrom 1996 (Hydrovatus adults)
Larson & Storey 1994 (Carabhydrus adults) |
