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

Gyrinidae

Major Group: Insecta
Order: Coleoptera
Family: Gyrinidae

Descriptive Features:
Adults

  • head not exserted
  • eyes divided into dorsal and ventral portions
  • antennae very short and thick, with less than 11 segments, the first of which is very large, length always greater than 1 mm, entirely or almost entirely glabrous
  • dorsal surfaces rarely with erect, fixed sensory setae
  • elytra truncate exposing most of one abdominal tergite
  • abdomen with ventrite 1 divided into 2 or 3 parts by hind coxae
  • prothorax with pair of notopleural sutures (distinct from sharp lateral margins) separating notum from externally visible pleuron on each side
  • metasternum without transverse suture, if suture present, then elytra without regular puncture rows
  • mesocoxal cavities open laterally (partly closed by mesepimeron)
  • metacoxal plates absent or consisting of narrow mesal portion only, not concealing basal ventrites or femora
  • metacoxae lateral portions longer than metasternum
  • metacoxae extending laterally to meet elytra, so that junction of metepimera and first ventrite is not visible
  • tarsi always 5-segmented
  • fore tibia without antenna cleaner
  • forelegs long, raptorial
  • mid- and hindlegs short, paddle-like
  • size: 3.5 - 15.0mm
    Larvae
  • maxillary palp, 4-segmented
  • mandibles narrow and falcate, with internal perforation
  • labial palps 3-segmented
  • labrum completely fused to head capsule
  • antennae longer than head width
  • body long, thin
  • abdominal segments 1-8 with lateral gills
  • abdominal tergum 9 without paired urogomphi, sometimes with 2 pairs of gills
  • abdominal segment 10 not or only slightly longer than 9, with 2 pairs of hooks at apex
  • legs 6-segmented, including pretarsus (claws)
  • size: up to 20mm
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    Gyrinidae larva

     

    Aulonogyrus strigosus adult

    Taxonomic Checklist: Genera
    Aulonogyrus strigosus
    Fabricius
    Dineutus 2 species
    Gyrinus convexiusculus MacLeay
    Macrogyrus 15 species

    Distribution: Australia wide

    Sensitivity Rating: SIGNAL grade 4

    Functional Feeding Group: predators

     

    Murray River at Cottadidda State Forest, NSW

    Ecology: Instream habitat: Gyrinid beetles occur at the edges of small lakes, in ponds, small dams, and within slow flowing, sheltered sections of creeks and rivers. Adults of Gyrinidae species are the only beetles to inhabit the water surface in both lotic and lentic habitats.
    Feeding ecology:Adults are predators on insects which have fallen into or have become trapped within the water surface film. They locate prey using a specialised organ, within the antennal pedicel, which is sensitive to surface waves. Larvae are bottom dwelling predators and feed on a variety of soft-bodied animals e.g. worms, chironomid larvae or odonate nymphs.
    Habit: Gyrinid adults are commonly known as ‘whirligig beetles’ reflecting their habit of rapidly skimming across the water surface in a circular pattern. They are usually active during daylight and found in small to large groups until they are disturbed, when they will actively seek cover in vegetation. The circular swimming pattern 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 secreted by pygidial glands. Eyes of adults are separated into upper and lower pairs allowing the beetles to see above and below the water simultaneously. Larvae remain submerged through all instars and obtain oxygen from the water through abdominal gills.
    Life history: In North America gyrinid beetles copulate on the water surface and then the female lays her eggs on stems of emergent vegetation a few centimetres below the waters surface. After hatching larvae pass through two to three instars. The final instar larvae climb onto emergent vegetation or crawl onto shore where they form a mud or sand cocoon for pupation.

     

    Information Sources:

    Watts 2002, Lawrence & Britton 1991, Williams 1980, Gooderham & Tsyrlin 2000, Lawrence et al. 2002a
    Key to Genera: Watts & Hamon 2010 (adults, larvae – excluding Gyrinus), Watts 2002 (adults, larvae - Aulonogyrus & Macrogyrus not separated)
    Key to Species:  Watts & Hamon 2010 (adults, larvae)

     

     

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