Water Scorpion (Laccotrephes tristis)

The Water Scorpion (Laccotrephes tristis) is found throughout Australia. They are carnivorous insects that hunt near the water surface. Usually found in shallow stagnant and slow-moving water. They can be found in gorges and waterholes in Central Australia. On occasion they have been found in swimming pools. How they get there is unknown.

The only leaf-shaped water scorpion species in Australia is Laccotrephes tristis. There are other, sort-of leafy-looking species, like Austronepa and Goondnomdanepa, but they are not as broad, or don’t have as long breathing tubes.

Russell’ Yong, Entomology Australia “Invertebratology”, Facebook

Water Scorpion is an air breathing aquatic insect that can be found around mainland Australia, usually living on the edges of shallow pools or creeks.

They have six legs and a long thin structure attached to its rear end. This thin needle like appendage is used for breathing, a bit like a snorkel. The Water Scorpion breathes by trapping an air bubble in tiny water-repellent hairs between its forewings and abdomen. The hairs connect to the snorkel and when the air bubble is almost depleted, the Water Scorpion returns to the surface, sticking its snorkel out, through which air seeps into the snorkel in a process called diffusion, thereby replenishing the air bubble.

The Water Scorpions are known as ambush hunters, often hiding under the vegetation in shallow water. When its prey, usually a small aquatic creature such as a bug, fish or freshwater prawn swims by, the Water Scorpion lashes out with its pincer-like appendage grasping the unsuspecting aquatic creature with its front legs. The Water Scorpion then plunges its rostrum or ‘nose’ into the body, injecting enzymes that will partially digest the prey. It then sucks the resulting body matter up through its rostrum.

The Water Scorpion pictured here was rescued from a salt-watered swimming pool in Alice Springs and relocated to a fish pond.

It is interesting to see the colour difference when we relocated the Water Scorpion from the swimming pool to the fish pond.

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Many thanks to Russell’ Yong from Entomology Australia “Invertebratology”, Facebook group for assistance with identifying this Water Scorpion species.

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• Scientific classification
• Kingdom: Animalia
• Phylum: Arthropoda
• Subphylum: Hexapoda
• Class: Insecta
• Informal: Pterygotes
• Order: Hemiptera
• Suborder: Heteroptera
• Infraorder: Nepomorpha
• Superfamily: Nepoidea
• Family: Nepidae
• Subfamily: Nepinae
• Tribe: Nepini
• Genus: Laccotrephes
• Subgenus: infrageneric Laccotrephes
• Species: Laccotrephes tristis

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InsectsBees Beetles Blattodea Butterflies Coleoptera Cicada Crabronidae Diptera Dragonflies & Damselflies Formicidae Hemiptera Heteroptera (True Bugs) Mango Planthopper Moths Orthoptera Orthopteroid Processionary Caterpillar Stink Bugs, Shield Bugs and Allies Syrphidae Wasps Water Scorpion (Laccotrephes tristis) Witchetty Grub