The Tiger Beetle

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The Tiger Beetle Pseudotetracha whelani on Lake Gairdner, South Australia

Driving along a remote outback road with dust bellowing up into the clear night sky, the rocky hills are lit with the faint blue light of the moon which slowly wanders across the sky. We arrive at our destination and turn the head lights off to be confronted by a wide glistening expanse before us, a surface encrusted with salt crystals stretching almost to the horizon.

This is Lake Gairdner, the third largest salt lake in Australia, which is accessible through Mt Ive Station in the Gawler Ranges in South Australia. Salt lakes are one of the most bizarre and beautiful landscapes I have ever visited. There is such an expanse of flatness which you rarely encounter in day to day life, and the brightness of the sunlight reflecting off the surface during the day can be astounding. They seem like a weird moonscape, apart from I imagine the moon is not as flat. At night, with a clear sky, they are breath-takingly beautiful. The moonlight glistens off the salt crystals and the stars above don’t feel so far away.

While wandering around the edge of Lake Gairdner admiring the wide expanse of sky studded with the diamond like stars, something speedily scuttled past my foot. My torch zips about across the salt, a flash of iridescent green, then gone into the darkness. My light finally locks onto one of these creatures to reveal a large brilliant green shining beetle with long yellow legs and mandibles longer than its head.

This voracious looking creature is a tiger beetle of the genus Pseudotetracha, which is found mainly on salt lakes, and unsurprisingly is a nocturnal predator. These beetles dig deep burrows where they spend their scorching outback days, and then come out at night to hunt. When I say speedily scuttled past my foot I was not joking, Pseudotetracha whelani, the species we encountered, has a body length of around 17.5 mm and run at a maximum of 0.72 m per second (2.6 km/h). That’s 41 body lengths per second. This is like me running at about 265 km/h! Another Tiger Beetle Cicindela hudsoni (approximately 21 mm long), is thought to be the fastest running insect in the world and can run at an astonishing max speed of 2.49 m per second (9 km/h) and 120 body length per second. C. eburneola although having a lower max velocity (1.86 m/s) can move at 171 body lengths per second. These are some amazing stats.

The group of Tiger Beetles within the genus Pseudotetracha appears to have evolved into several different species associated with Australia becoming more arid between 10 – 5 million years ago. As Australia dried up, the ancestral beetle populations became isolated from each other at different salt lake drainages. They begun to change over time eventually becoming different species. The salt lakes act like islands surrounded by water where the area in-between the habitable island or lake is mostly impassable and the beetles from one lake cannot come into contact with beetles from another and breed. Despite being able to run fast, many of these Tiger Beetles are poor fliers or are unable to fly, like P. whelani the species I saw, contributing to their isolation.

Salt lakes are stunning places to visit, and Australia has a good number of them. Being out on one at night you may encounter some of these speedy beautiful Tiger beetles going about their nightly hunting. However, these extremely interesting insects are not just found on salt lakes but in all sorts of habitats all over the world. So keep an eye out for these voracious and fascinating beetles.

I would also like to thank Dr Peter Hudson from the South Australian Museum for verifying the ID of this Tiger Beetle given the location and photograph. Very much appreciated.

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Lake Gairdner, South Australia

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