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Ranatra

Genus of true bugs

  • 5 min read
  • 2 chapters
Water stick-insect , at Itami City Museum of Insects
Daiju Azuma · CC BY-SA 2.5

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Through Predation

Lab · Class 8–12Ecosystem DynamicsLab · Class 12Population Ecology

These brown insects are primarily found in stagnant or slow-moving water like ponds, marshes and canals, but can also be seen in streams. Exceptionally they have been recorded from hypersaline lakes and brackish lagoons.

Biology

The front legs of bugs in Ranatra are strong and used to grasp prey. They typically eat other insects, tadpoles and small fish, which they pierce with their proboscis and inject a saliva which both sedates and begins to digest their prey. They are sit-and-wait predators that reside among water plants and position themselves head-down with their grasping legs extended out to surprise passing prey. At least one species will also swim in open water at night to catch zooplanktonic organisms. Like other members in the family they have a long tail-like siphon, or breathing tube, on the rear end of their body. The adult body length is generally 2–6 cm (0.8–2.4 in) depending on the exact species, and females average larger than males of the same species. The siphon is typically almost the same size, but varies from less than half the body length to somewhat longer. Two of the largest species are the East Asian R. chinensis and South American R. magna. Ranatra do have wings and they can fly.

The adults are active year-round, except in extreme cold. Their eggs are positioned on plants just below the water surface, but in some species they can be placed in mud. The eggs typically take two to four weeks to hatch and the young take about two months to mature.

Among the four genera in the subfamily Ranatrinae, Austronepa and Goondnomdanepa are restricted to Australia. Cercotmetus from Asia to New Guinea resembles Ranatra, although the former has a distinctly shorter siphon.

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