Bug of the Month

by Jessie
Publish date
1 August 2011
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The stars of the Bugs Alive! aquatic display Green Diving Beetles (Onychohydrus scutellaris) are remarkable for their ability to store air and dive underwater to hunt food and find mates. They are found Australia-wide and on warm nights are attracted to lights. Recently on the Gold Coast there was a report of thousands of these beetles coming into the lights on the foreshore and the ground around the lights was a black moving mass.

green diving beetle Adapted to a life in the water, Green Diving Beetles have streamlined bodies, paddle like hind legs with swimming hairs and an amazing ability to store pockets of air so they can dive under water for extended periods of time.
Image: Alan Henderson
Source: Museum Victoria

Although sometimes they can be locally common they are predators and tend to live in water bodies, like dams and lakes at densities that do not deplete prey numbers too much; once prey numbers get too low, these beetles fly to a new water body and establish themselves there.

Adults lay their eggs in the water where tiny predatory larvae hatch out. The larvae spend their entire larval stage in the water before digging into the muddy banks of ponds and pupating. Once mature, the adults can either hang out where they emerged or fly and disperse to other areas where the food source is more readily available.

Over the last 12 months in Victoria, like many parts of Australia, has had increased rainfall which allows the beetles to disperse and breed at a greater rate than over the last few years of drought. Live Exhibits staff are predicting a great summer for Green Diving Beetles and they may turn up a bit more often in the Melbourne metropolitan area. Live Exhibits staff will be heading out equipped with torches, nets and waders to see if we can hunt down these incredible animals.

Green Diving Beetles
Green Diving Beetles can be voracious feeders; here a group of them are feasting on a dead fish at the Melbourne Museum.
Image: Alan Henderson
Source: Museum Victoria

These beetles are active predators and scavengers and add a great degree of movement and colour to our Bugs Alive! display. As they forage they constantly return to the surface of the water to replenish their air supply which they hold under their elytra (wing covers). They eat other aquatic invertebrates and in the wild will sometimes attack vertebrates such as small fish and tadpoles.

Next time you are in Bugs Alive! check them out in the aquatic tank. They spend a fair bit of the day sitting motionless clinging onto foliage but once they get moving they can certainly swim fast.

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Updates on what's happening at Melbourne Museum, the Immigration Museum, Scienceworks, the Royal Exhibition Building, and beyond.