| Positive | Menk | On Dec 31, 2007, Menk from Darling Downs
() wrote:This interesting and iconic insect is rarely encountered in the Australian bush. It is usually found at moderate to high elevation along the length of the Great Dividing Range, from near Herberton to Tasmania. It has also been found occasionally in pastures at relatively low altitude in western areas, as far west as Nyngan in NSW, and near Moonie and Chinchilla in Qld. It is known to inhabit the Carnarvon Ranges.
In SE Qld the species prefers Themeda triandra (kangaroo grass) grasslands in open eucalypt and grasstree forest, often above elevations supporting rainforest or vineforest. It is often found above cliff lines and near rocky scree slopes. Further west it may be found in hilly wooded country, only rarely on the plains. It can sometimes be locally common, but is most often encountered as isolated individuals. The females are the most commonly seen.
The photos by kennedyh show the male of the species which has wings. The female has no wings, only small wing covers which are grey and crinkly and look like half peanut shells.
I have included some photos here of the female. Unlike the male, the female does not look much like a grasshopper. She is dumpy and has long, spidery legs that seem out of proportion with her large body. When disturbed, she lifts her wing covers and arcs her body to expose the bright red and blue stripes on her back and the bright orange collar around her neck. She may do a kind of dance when disturbed, standing right up on her thin legs, and moving around in half circles, or in a kind of staggery manner. They are completely harmless and all bluff, but I am sure some people have mistaken them for wasps, spiders, or hornets. I hope to include some more photos in future, showing the remarkable defense posture of the female.
The male mountain katydid calls from late afternoon to just after dark, and the sound is a bit like soft yet rapid machine gun fire. The call is typically one long burst, followed by two shorter bursts, with the final burst often very short. They occasionally call throughout the day, generally resting head down on a low branch in a prickly bush to avoid detection. The male is generally reluctant to fly, but if disturbed can fly 10-20 metres, before dropping into another bush. In cool or cloudy weather, the male may rest motionless on the ground, and look just like a fallen leaf. As with the females, it too is fond of basking in sunny spots.
It is thought that the males have poorly defined territories, in which a small "harem" of the ground-dwelling females roam. But little is known about the dynamics or social structure of their colonies. The females seem to be attracted to the male's call, which may help to keep them nearby. At the same time, the ground dwelling females, though mute, may be constantly seeking out new food sources. The male will sometimes chirp as if in alarm when a potential predator comes nearby.
I have estimated that their territories may cover about a 10-30 metre radius. Males probably compete with other males for mates, and we can presume that the one with the loudest and clearest call may be the one that wins the most females. It is possible that the males die first towards the end of the season, allowing the females to wander off in search of good localities to deposit their eggs. The females large abdomen supports large numbers of eggs. They always lay their eggs (which are beige coloured and the size and shape of Acacia seed) well away from their host plants, and in a spot where fire cannot reach eg. around rock scree, overhangs, or in rainforest.
I have only recently discovered that they often lay their eggs in the topsoil. They dig a small hole, lay the eggs, then carefully bury them and smooth the surface off meticulously with their tiny feet. Each female is capable of laying dozens of eggs in her lifetime. The eggs can take many months, possibly even years to hatch, waiting until conditions are just right. Only a small number of the ant-like young (called nymphs) will ever make it to adulthood.
It is vital to preserve these insects in Australia, not only because they are an iconic species, but because they serve a valuable economic purpose. Their favourite food source is Asteraceae (the daisy family), with a preference for the more weedy species. They love fireweed. They will eat off the flowers, leaves and buds, and even the seeds, of these plants. Both the native fireweed Senecio lautus, and the troublesome exotic Senecio madagascariensis are high on their menu. The introduced ragwort pest, Senecio jacobaea, is one of their favourite foods. The mountain katydid is one of only a few species of animal that can eat this noxious triffid without suffering any ill effects. They will also eat many of the native Senecio species, as well as Leiocarpa species (Billy Buttons) and probably the common Chysocephalum apiculatum. They also love Achillea milleflorum (yarrowherb). I once observed a female katydid consume an entire yarrow leaf in five minutes flat!
They have also been observed eating the leaves of blue heliotrope weed (Lamium amplexicaule), which can be a serious weed in pastures and toxic to livestock.
Unfortunately this species has gone into dramatic decline in recent decades. Loss of habitat due to development and weeds (Lantana camara in particular) is largely responsible. Introduced fauna (mice, rats, cats, foxes, cane toads) have almost certainly taken a heavy toll as well. They love to bask in the early morning sun, so they may venture on to walking tracks in national parks. They may even stroll on to suburban lawns that are located near large forest areas. When walking at high elevations it always pays to watch where you are treading.
It is vital to preserve large areas of Themeda grassland, particularly those on the Dividing Range in open eucalypt forest. This is a community on which the Acripeza largely depends in Queensland. In southern states, they may rely on Poa grasslands.
Ironically, some of the weed eradication programs in Victoria have been so successful at ridding large areas of the ragwort, that the katydids have gone into serious decline in many areas. It is probable that the ragwort had smothered out the native Senecio species, and even though it provided an excellent surrogate food source for the katydid in the early days, its eradication lead to an immediate and dramatic decline in the katydid population. Drought and introduced predators have further hindered their recovery.
The unusual plants that the mountain katydid eats would be unpalatable or even toxic to other animals. It has the ability to store these toxins in its own body tissues, making it untasty if grabbed by a predator. Still many do succumb to predation. Some birds and lizards may be able to cope with the toxins or have perhaps learnt to eat only selective parts of the insect . I suspect that many of the feral animals, like cats, may kill these insects out of instinct or curiosity, even if they find them distasteful. Cane toads may prove to be a major predator, but more study is needed.
Apart from their bluff response and the toxins stored within their tissues, the mountain katydid is completely harmless. Needless to say it is impossible for this katydid to transfer any toxins to humans through the process of handling. Never has there been a more harmless and remarkable insect! |
