Major group: Insecta
Order: Coleoptera
Family: Spercheidae (formerly within Hydrophilidae)
Genus: Spercheus
This family is represented by a single genus worldwide, Spercheus. |
Descriptive Features:
Adults
antennae 7- to 9-segmented with 3- or 4-segmented club
2nd segment of maxillary palpi slender
body rounded, dull brown
elytra with distinct raised areas, exposing less than 2 complete abdominal tergites
abdomen with more than 3 ventrites
ventrite 1 not divided by hind coxae
pleuron reduced and concealed
prothorax without notopleural sutures, ventral portion of the notum, (hypomeron) on each side joined directly to the sternum by notosternal suture
basal segment of hind tarsi shorter than 2nd
size: <5mm
Larvae
distinctive larva with large head, strongly tapered abdomen and lateral processes on first 8 abdominal segments
labrum completely fused to head capsule
labial palps 1-segmented
apex of mandible bidentate
maxilla with distinct mala
stipes wider than long
gular sutures separate
1st segment of maxillary palp, with large, digitiform appendage
abdominal tergum 8 usually subterminal, forming with segment 9 a spiracular chamber housing enlarged 8th spiracles
legs present
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Spercheus larva |
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Spercheus adult |
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Taxonomic Checklist: Species
Spercheus platycephalus MacLeay
Spercheus wattsi Hebauer |
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Distribution: N Aus, E Qld, E NSW, E Vic, N WA
Sensitivity Rating: none; formerly within Hydrophilidae - SIGNAL grade 2
Functional Feeding Group: filtering collectors |
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Logan Home Lagoon, Brisbane Qld |
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Ecology: Instream habitat: Spercheus beetles inhabit shallow, still waters such as ponds, dams, bore drains, stock water troughs or slow moving creeks and streams, staying close to the underside of the waters’ surface.
Feeding ecology: Adults of Spercheidae are known worldwide as highly specialized filter feeding scavengers, feeding on plants and decaying plant matter. Spercheidae larvae are known worldwide as filter feeders of detritus with a specific mechanism for carrion, but in Australia, larvae are recorded as predators, feeding on a variety of snails, worms, small crustaceans and insect larvae.
Habit: Adults and larvae are poor swimmers that walk along the underside of the surface film.
Life history: Little information is recorded for Australian species of Spercheus. In Central Argentina, study on S. halophilus demonstrated that females enclose their eggs within silken egg cases and carry them on the ventral side of the abdomen, keeping the egg cases in place with their hind legs. When the larvae hatch, the female drops the empty egg case. The spercheid life cycle is possibly short with the egg phase lasting about four to five days; first instar four to six days; second instar six to seven days. Unfortunately, pupation did not take place in this study, so the duration of the last larval instar is unknown. |
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Information Sources: Watts 2002, Calder & Wells 2004, Bernhard et al. 2006, Archangelsky 2001
Key to Species: none |
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