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 Major Groups | Insecta (insects) | Coleoptera (beetles)
 

Coleoptera (beetles)

Major Group: Insecta
Order: Coleoptera 

Descriptive Features:
Adults

  • mouthparts biting, mandible and maxilla developed for grasping and chewing
  • wings present, animals capable of flying or gliding
  • forewings modified to hard elytra meeting along the midline of the body when at rest
  • hindwings membranous, when present
  • total length:
    Larvae
  • wings absent
  • mouthparts conspicuous and biting, mandible and maxilla developed for grasping and chewing
  • caudal filaments, caudal gills and caudal processes usually absent, however Dytiscidae larvae have 2 long caudal filaments
  • anal segment with or without paired terminal lobes
  • legs absent or 3 pairs of jointed legs on thorax
  • abdominal lateral processes usually absent, however Hydrophilidae: Berosus and Gyrinidae larvae have paired processes on abdominal segments 1-7 and 1-8 respectively
  • total length:
  • Taxonomic Checklist:

    Families

    Carabidae
    Chrysomelidae
    Curculionidae
    Dytiscidae
    Elmidae
    Georissidae
    Gyrinidae
    Haliplidae
    Heteroceridae
    Hydraenidae
    Hydrochidae
    Hydrophilidae
    Hygrobiidae

    Limnichidae
    Nanophyidae
    Noteridae
    Psephenidae
    Ptilodactylidae
    Scirtidae
    Spercheidae
    Sphaeriusidae
    Staphylinidae
     

      

    Distribution: Australia wide

    Sensitivity Rating: SIGNAL grade 5

    Functional Feeding Group: predators, scrapers, shredders, macrophyte piercers, gathering collectors, filtering collectors

    Ecology: Instream habitat: Coleopteran adults and larvae are widespread, numerous and found in a variety of habitats. Not all families included in this Guide are fully aquatic through all life stages and for some families there is only a single genus that has aquatic stages. However those adults that are deemed to be terrestrial or semi-aquatic are generally restricted to damp or riparian habitats. Aquatic adult and larval beetles are found in a wide range of freshwater types, from stagnant peat bogs to fast flowing rivers, and inland saline lakes. They are collected from many different instream habitats such as; on aquatic or riparian vegetation either above or below the water surface, in riffles where the water is clear with high oxygen content, clinging to submerged tree branches or to moss covered rocks, under submerged objects, dwelling in the interstitial spaces of the substratum, in burrows in the bank or rotting woody debris, amongst pebbles, gravel, sand, mud, silt, peat and other organic debris.
    Feeding ecology: All functional feeding groups are represented across aquatic and semi-aquatic beetle adults and larvae. Coleopteran predators feed on soft-bodied insects, crustaceans, molluscs, worms, leeches, tadpoles and small fish. Generally the size of the beetle determines the size and type of the prey. The feeding method may differ between adults and larvae of the same species. Adults and most larvae have biting mouthparts and ingest solid and liquid food. A few larvae have closed mouth openings and so use mandibular channels to inject digestive enzymes into their prey and then suck up the resulting fluids. This is similar to hemipteran (bugs) feeding. Some predatory beetles are nocturnal hunters, sheltering in the daytime. Phytophagous (plant eating) beetles feed on leaves and stems of macrophytes or on submerged roots, even burrowing internally to obtain food. In some cases, the feeding activity of larvae results in rotting of the surrounding plant tissues and can result in plant death. Wood dwelling beetles feed on waterlogged wood and the associated algae and fungi. Herbivore shredders and piercers feed on various types of green algae and other plant material with some beetles able to suck algal cells or plant tissue through perforations in their mandibles. Scrapers feed on the biofilm associated with stream rocks, macrophytes and wood. Collectors feed on diatoms, and organic debris. Scirtidae larvae as well as Spercheidae adults and larvae are the only coleopteran filter-feeders, feeding on detritus or possibly small crustaceans and insect larvae in case of Spercheidae larvae.
    Habit: Adults may be wing-dimorphic however some species are flightless with the elytra almost permanently bonded. Some adults, in particular semi-aquatic and terrestrial species, are typically nocturnal and are readily attracted by light traps. However, other adults are active during daylight until they are disturbed, then they will actively seek cover in vegetation or under rocks. Totally aquatic beetles breathe by various means, such as; using spiracles or gills to breathe underwater, tapping into submerged plants with hollow stems, using a siphon located at the tip of the abdomen to draw in surface air, storing air in the sub-elytral cavity and between the metacoxal plates or as a bubble beneath the elytra or as a plastron (thin layer of oxygen around the abdomen). Psephenidae larvae may be unique among Australian aquatic beetles as they breathe dissolved oxygen in the water through a tuft of anal gills but they can also breathe atmospheric oxygen when out of water for several weeks before pupation. Whilst some beetles have swimming hairs on their hind legs to enable active swimming, not all beetles can swim, others crawl on submerged substratum or upside down just under the water surface. Some beetles are heavier than water and must climb or swim to the surface; others are buoyant forms which put in effort to stay submerged. Hydraenidae: Hydraena beetles crawl on vegetation and merely float to the surface if they become dislodged. Staphylinidae: Stenus and Paederus adults are able to run on the surface of the water. The highly specialised adults of Gyrinidae swim in a circular pattern which comes from having flattened, paddle-like mid- and hind-legs that are shorter than the forelegs. The beetles are able to skim the water surface with the aid of surfactants. Their eyes are separated into upper and lower pairs allowing the beetles to see above and below the water simultaneously.
    Life history: There is little life history information available for many Australian coleopteran species, especially aquatic species. In general terms, the aquatic larval stage is the longest part of the life cycle and the pupal stage the shortest. For all known life histories, final instar larvae leave the water to pupate in a damp mud, sand or a silken cocoon. The new adult then either returns directly to the water or remains in the riparian vegetation and litter. Adults tend to mate above the water’s surface on the emergent portions of macrophytes or on the water surface itself. Females lay their eggs within plant stem tissue or within a densely woven silk cocoon generally attached to submerged substratum. In a few families there have been cases of maternal care for caches of eggs recorded. Beetles are found in all life stages all year round although each family usually has a specific emergence time that relates to water availability and temperature.
     
     
    Information Sources: Lawrence & Britton 1991, Watts 2002, Gooderham & Tsyrlin 2002, Walton 1987, Glaister 1999, Davis 1998, Lawrence et al 2000, Matthews 1980, Williams 1980 and information sources listed on family pages 
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