Image: Beetle

Beetle

Beetle, line drawing.

Creator:
Andrew Howells
Rights:
© Australian Museum

Notes

Beetles, which include weevils, belong to the Order Coleoptera.

What do beetles look like?

Size:
  • 0.4 mm - 80 mm in length.
Body:
  • Greatly variable in shape.
  • Pronotum (segment behind head) usually large.
  • Generally appears hard.
Antennae:
  • Form and length highly variable.
Eyes:
  • Variable ranging from so large that they meet in the middle to no eyes at all.
  • For most species are large and well separated.
Mouthparts:
  • For chewing or munching.
  • Held in front at rest.
  • Some very small beetles have mouthparts forming a sucking tube, while weevils have mouthparts on the end of a nose.
Wings:
  • One or two pairs if present, though most have two pairs.
  • Forewings (elytra) hardened and rigid, cloudy and with no visible veins.
  • Hindwings are membranous and clear.
  • At rest, forewings are held flat over body, meeting at midline.
  • Hindwings are usually folded and hidden.
  • The wings generally cover the abdomen but some species of beetle have shortened wings.
  • Some flightless species have the forewings fused together so it does not appear that there are any wings at all.
Limbs:
  • Six legs.
  • Highly variable depending on the lifestyle of the beetle, for example some beetles have strong slender legs for running, while others such as dung beetles have spade-like legs for digging.
Abdomen tip:
  • Cerci (tails) absent.

Where are beetles found?

  • Practically anywhere including marine environments.
  • In houses amongst foodstuffs, furnishings and wooden objects.

What do beetles do?

  • They are solitary or rarely form groups. They maybe found in groups on localised food sources or when mating.
  • A few beetles are external or internal parasites of other insects while some such as rove beetles are parasitoids.
  • When disturbed they might remain still, run, fly, clamp down on surfaces, drop to ground, burrow, jump, make noise or spray chemicals.
  • Beetle forewings are not used for flight - so they may be held in place, upright or out to the sides.
  • They are strong fliers capable of covering long distances.
  • Their feeding habits are very diverse.
  • Many are experts at camouflage. Some have colours, patterns, structures or behavioural traits that allow them to blend in with their surroundings.
  • Some look and behave like other insects such as ants, wasps and termites.
  • They are active during the day or night.

What looks similar?

  • Cockroaches are often confused with beetles. They can be distinguished from beetles as their forewings overlap rather than meet. If the wings are absent, then cockroaches can be distinguished by the presence of cerci and a pronotum (segment behind head) that overhangs the body and the head.
  • Some groups of True bugs look very much like beetles. All true bugs can be distinguished by their mouthparts, which are tube-like for sucking. Otherwise true bugs can be separated from beetles by their forewings, which tend to overlap and are partially see-through.
  • Earwigs can be confused with rove beetles (family Staphylinidae). Rove beetles have small cloudy forewings with clear membranous hindwings folded underneath, similar to earwigs. But they lack the fully developed abdominal forceps as seen in earwigs.
  • Flies can be confused with wood-boring beetles (family Lymexylidae). The forewings of these wood-boring beetles are sometimes reduced to tiny pads and the hindwings are fully exposed which gives them the appearance of having only one pair of wings. Flies have a reduced hindwing and a fully functional forewing.

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Tags beetles, weevils, insects, invertebrates, identification, Bugwise,