Water striders are the most conspicuous element of the semi-aquatic bug fauna of Australia. Belonging to the family Gerridae, they are adapted to their life on the water surface due to their distinctly elongate mesothorax and long and slender middle and hind legs. This allows them to “skate” or “jump and slide” in a very characteristic way on the water surface and is aided by the hydrofuge or water shedding properties of the legs. One often first notices them because of a disturbance on the water surface or notices the “dimples” in the water surface created by the legs, or the shadow of those dimples on the bottom of the water body. Tenagogerris euphrosyne is a species common along the east coast from Cape York in Queensland to western Victoria, with this picture taken at a fresh water pool in Sydney Bushland. Here the male is riding on the female’s back in what is known as “mate guarding”: after mating the male remains with the female so that no other males can mate with her. It is a characteristic water strider behaviour and still allows them to move freely on the water surface. Depending on the time of the year, populations can consist of both winged and wingless adults as well as nymphs, with adult size of this species ranging from 7 to 10 mm body length. The winged forms are quite capable of flight and allow the species to locate another body of water if their present one dries up. Water striders are opportunistic predators and scavengers, preying on anything that falls to the water surface. The strong proboscis as seen in the picture allows them to pierce their prey and suck out the juices. Words by Tom Weir, Honorary Fellow, Australian National Insect Collection, CSIRO, Canberra For more images and information, visit http://photography.irwig.com/ and follow the ‘strider’ link.
Rain made a welcome comeback to Australia in 2016 after several years of deepening drought. But Tasmania and the Top End were among several places that did not fare so well.
Known as a ‘red tide’ by day, the microalgae Noctiluca scintillans, known as ‘sea sparkle’ emits a bioluminescent blue glow when disturbed at night. Over the last week, residents of Hobart, Tasmania, have been treated to a light show on the Derwent River, mostly around the South Arm Peninsula, as the dinoflagellate bloom has washed ashore. The bloom can be deadly to fish if it accumulates and gives off ammonia as the microalgae die.