Autumn in the mallee
A travel story
In April this year we made a brief stop in the mallee in north-west Victoria, on our way to visit family in South Australia.
Our stay at the conservation property ‘Explore the Mallee’ was wonderful … and all too brief. We learned about the extraordinary breeding behaviour of the iconic Malleefowl from dedicated naturalists Louise and Michael. The rich bird life on their property is certainly reason enough to take a tour with them. Yet we were equally intrigued by the insects and spiders … including the many and varied ants.
We plan a return visit in spring one year, in search of other mallee insects.
First, the ants
Among the most obvious and numerous insects were the ants. Here is a small sample of the ground-level action.
Meat ants (Iridomyrmex purpureus)
Large with purple heads, extremely numerous, highly responsive, and day active.
Green-head ants (Rhytidoponera metallica)
Metallic and armoured, few in number, nesting among low vegetation.
Titan Pony Ants (Rhytidoponera mayri)
Large and with very long legs and a wrinkled appearance.
Shield ants (Meranoplus oceanicus)
Unusual, stout legs, slow-moving … and utterly endearing.
Meranoplus oceanicus … (see my working notes page for the detailed logic behind my suggested species ID)
Mallee Black Sugar Ant (Camponotus cinereus amperei)
Very active, shiny, black ants … often holding their gasters in upright.
Desert Funnel Ants (Aphaenogaster barbigula)
Small, fragile, pale brown ants … but very rarely do they venture above ground. They are better known by their distinctive nests than by the ants themselves.
A bit of a mystery
Looks a bit like an Aphaenogaster funnel, but the entrance is smaller. And the ants moving to and from are certainly not funnel ants!
Even more ants!
The species listed above are tiny sample of ant diversity in the mallee. Here are a few more, but details will have to wait for another time. Perhaps a return trip. In the meantime, a quick look at iNaturalist sightings for the region gives some idea.
A variety of other insects
While the ants were fascinating, the star of the show for us was this large, green, spotted katydid. We’ve never seen one before, and she was most cooperative … out in the sun, on the sand, allowing us to crowd around for a shot (well, several shots). She’s the Spotted Predatory Katydid (Chlorobalius leucoviridis). The species is reportedly ‘wholly nocturnal’ (ref. 9), but I guess anyone can be late getting home. She may have spent the night laying eggs in the soil nearby (ref. 9, p.11).
Chorobalius leucoviridis (see iNaturalist record)
Paul did a bit more reading about this species and learned how these predators can lure cicadas by mimicking their calls – a behaviour known as ‘aggressive mimicry’ (ref. 12). In summary:
In many species of inland cicadas, the female cicada responds to a male’s call with a sound of her own. She makes this by flicking her wings. The female’s call is quite ‘nondescript’, so to work she makes it within 100milliseconds of the male. Timing is all!
Male cicadas walk or fly toward the female, then courtship and mating take place. All is good.
However, the katydids (both male and female) can make a similar sound … and they do so in response to the calls of various species of male cicadas.
The male cicadas are fooled and approach the katydid … only to become the predator’s next meal. Aggressive mimicry indeed!
A second highlight was the spectacular blue of a newly-laid ootheca … and its equally spectacular (and large!) owner. This species of grass mantis, Achimantis quinquelobata, is typically found in woody shrubs, although occasionally in grasses (ref. 10). It is widespread throughout the more arid regions of the mainland. Females range considerably in size, with a body length anywhere between 8 and 13 centimetres. This lovely girl was large, but we didn’t take a measurement. She was busy, after all.
I was witness to yet another exciting event. As I prowled the track around the funnel-ant nests, I noticed a female velvet ant (Eurymutilla) digging in the sand. These little wasps are ectoparasites of a range of other hymenopterans, especially ground-nesting bees, crabronid and vespid wasps. Their larvae develop safe inside the pre-prepared nest, at the expense of the host larvae.
This flightless female was clearly seeking something when a winged male landed alongside her. She scurried off but he quickly caught her, and they rolled about for a few seconds. I’m not convinced the mating attempt was a success. If so, it was all over very quickly! Then again, I have read that such is sometimes the way of mutillids (ref. 11).
Then there were the myriad other orthopterans and other late-season insects. Species-level identification for some remains a work in progress.
Prowling spiders
Although we didn’t undertake a serious spider hunt, whenever we ventured out after dark there was something to find.
Finally, the birds
Most guests at Explore the Mallee are there for the birds. And it’s no wonder. We weren’t even trying particularly hard – given we were eyes-down hunting ants and other small critters – yet we were delighted with our sightings. The Pink Cockatoos were a real treat, and Bluebonnets a lifer for us!
Louise and Michael are custodians of the local nesting Malleefowl. They monitor the mounds, record breeding events, control feral pests … and share their knowledge with visitors like us. I was lucky enough to see a pair of birds just on dark, and watch as they flew to the top of a tree to roost – a first ever sighting of this roosting behaviour for Michael and Louise too, so there was considerable excitement!
As we were outside breeding time, the birds were not active at the mounds, but we did visit one for a quick look. Our guides even treated us to a close view of the large eggs. The mound contained several that were undeveloped and abandoned.
We look forward to a return trip one day.
References
Greensdale, P.J.M. & Halliday, R.B. 1983. Colony dispersion and relationships of meat ants Iridomyrmex purpureus and allies in an arid locality in South Australia. Insectes Sociaux, Paris. 30 (1): 82-99
Thomas, M.L. & Elgar, M.A. 2003. Colony size affects division of labour in the ponerine ant Rhytidoponera metallica. Naturwissenschafen 90, 88-92. https://doi.org/10.1007/s00114-002-0396-x
Gibb, H. 2005. The effect of a dominant ant, Iridomyrmex purpureus, on resource use by ant assemblages depends on microhabitat and resource type. Austral Ecology 30: 856-867
Heterick, B.E. 2009. A guide to ants of south-western Australia. Records of the Western Australian Museum, Supplement 76
Pamilo, P., Crozier, R.H. & Fraser, J. 1985. Inter-nest interactions, nest autonomy, and reproductive specialization in an Australian arid-zone ant, Rhytidoponera Sp. 12. Psyche 92(2-3) 217-236 available on ResearchGate
Hölldobler, B. 1988. Chemical communication in Meranoplus (Hymenoptera: Formicidae). Psyche 95(3-4), 139-151.
Andersen, A.N. 2006. A systematic overview of Australian species of the myrmicine ant genus Meranoplus F.Smith, 1895 (Hymenoptera: Formicidae). Myrmecologische Nachrichten 8, 157-170. available via AntWiki
Shattuck, S.O. 2008. Australian ants of the genus Aphaenogaster (Hymenoptera: Formicidae). Zootaxa 1677: 25-45 available via AntWiki
Rentz, D. 2010. A Guide to Katydids of Australia. CSIRO Publishing.
Milledge, G.A.1997. Revision of the tribe Archimantini (Mantodea: Mantidae: Mantinae). Memoirs of the Museum of Victoria 56(1): 1-63 available from the Museum’s site
Waldren, G.C. 2021. The Velvet Ants (Hymenoptera: Mutillidae): Systematics, Biology, and Biogeography of a Little-Known Family. All Graduate Theses and Dissertations. 8092. https://digitalcommons.usu.edu/etd/8092
Marshall, D.C. & Hill, K.B.R. 2009. Versatile aggressive mimicry of cicadas by an Australian predatory katydid. PLOS One 4(1): 1-8 open access