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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.
This Australian endemic is common and well known in most parts of Australia. Indeed, it is quite famous for the ability of colonies to rapidly dispose of large animal carcasses. Hence the common name 'meat ant'.
Meat ants, despite their name, are actually omnivores. Adults favour sugary liquids, such as those secreted by caterpillars and bugs. But they are also voracious collectors of protein to feed their young. Other invertebrates – dead or alive – are fair game. Was this mouse spider dead before the ants discovered it? Perhaps. Perhaps not.
Meat ants are notoriously aggressive toward other, day-active ant species. The Titan Pony Ant here didn't stand a chance.
Although they don't sting, these ants can give a painful bite.
No obvious mounds, just very circular holes. And rather a lot of them!
In many locations, meat ants build huge mounds. But not always. A colony of this species in a similar environment (Morgan, SA) had nest mounds that were low or entirely absent, with just a sparse cover of gravel and twigs (ref. 1).
This species favours open, warm, sites with some nearby trees and vegetation. And the mallee country, including the driveway into the house block, is obviously perfect for them.
Meat ants can form huge colonies. A single colony may have numerous nests, each with multiple entrances, and linked by very obvious trails (ref. 1).
Meat ant trails! These very obvious tracks linked nests and probably also led to favourite foraging areas, such as nearby shrubs and trees.
Green-head ants (Rhytidoponera metallica)
Metallic and armoured, few in number, nesting among low vegetation.
These tough-bodied little ants with the metallic sheen are a common sight across most of Australia. But unlike the meat ants, their colonies are often quite small. Indeed, we didn't see many individuals out and about. Also unlike meat ants, they can sting!
We found their nest on a little used track with a covering of dry vegetation. The low mound of excavated soil was less obvious than the collection of beetle carcasses surrounding it.
The literature on this species is extensive, their biology intriguing. Workers can mate and become reproductive, so colonies don't follow the typical 'single queen plus working daughters' model. And as colonies grow, the older workers tend to specialise in foraging while their younger nestmates stay home to care for the brood (ref. 2).
The nest opening was slightly obscured by grasses. Indeed, the reason we didn't see many active ants may be because they prefer to forage among vegetation. There they suffer less direct competition from their dominant neighbours, the meat ants (ref. 3).
Titan Pony Ants (Rhytidoponera mayri)
Large and with very long legs and a wrinkled appearance.
These are large, long-legged ants. Despite their rather fierce appearance, they were not at all aggressive toward me. I actually had to tease them out of their nest opening for a photo ... this one I enticed onto a stick.
A relative of the Green-head Ant, and like their relatives they have a sting. And wrinkled-looking skin ... 'rhytid' is a medical term for wrinkles ... making this genus quite recognisable in the field (ref. 4).
This species does build an obvious mound. The opening was a ragged tear in the soil, the galleries visible just below the surface. This is consistent with descriptions of newly-established colonies. Mature nests extend around a metre below ground (ref. 5), so the galleries are less obvious.
Mature colonies may contain hundreds of workers (ref. 5) ... but not the thousands of meat ant colonies!
Just inside the nest opening, several workers were carrying larvae from one part of the nest to another.
Shield ants (Meranoplus oceanicus)
Unusual, stout legs, slow-moving … and utterly endearing.
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Meranoplus oceanicus … (see my working notes page for the detailed logic behind my suggested species ID)
Rarely present in large numbers, these slow-moving ants are small and remarkably cryptic. When disturbed they 'play dead', curling into a ball with their antennae tucked away into grooves on their head. Soil caught in the hairs of their body provides further camouflage.
I'm sure I would have overlooked these little ants if Louise hadn't pointed them out to me. Their unusual appearance and behaviour had caught her attention some time ago, and she was curious to know more about them.
I was totally unfamiliar with them. Indeed, they tend to be uncommon in forests of the cool temperate zone (ref. 7). We have certainly never seen them in our home patch of SE NSW.
The broad plate covering much of the thorax lends the group their common name of 'shield ants'. It typically overhangs laterally and posteriorly, with various spines and translucent plates, depending upon the particular species.
Meranoplus nest underground in small colonies of around 150 workers. A colony usually has a single queen, but some small colonies may be queenless ... probably satellite nests arising from a 'queenright' colony, which may be many metres away (ref. 6)
Most shield ants are generalist omnivores, foraging on the ground and opportunistically taking seeds (ref. 7).
Mallee Black Sugar Ant (Camponotus cinereus amperei)
Very active, shiny, black ants … often holding their gasters in upright.
This posture, with abdomen raised vertically, is typical of the species. Despite appearances, they don't sting ... but they can bite.
This subspecies is common in arid and semi-arid woodlands across southern Australia (ref. 4).
Some Camponotus species nest in wood ... hence one of their common names, 'Carpenter Ants' ... but this colony was definitely excavating soil. The diggings forming the mound was evidence of a lot of past work.
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.
These distinctive, funnel-shaped nests are instantly identifiable as the work of Aphaenogaster ants.
They are large mounds, with very wide, round openings. Here my shoes provide scale (and I don't have small feet!)
Wandering insects that climb the outer wall are likely to fall directly into the opening ... and become food for colony. I'm not sure why one of these was closed. Perhaps an landslide caused by a passing large animal (not me!). Or maybe the ants sometimes close the burrow from within. A bit of a mystery, for now.
This species is typically found in habitats with at least some trees and shrubs, such as Callitris and mulga (Acacia) woodlands, and mallee (ref. 8). That fits with where I saw these ants, along a trail through quite dense bush.
Many mounds ... but not an ant in sight! Apparently this is quite typical for Aphaenogaster (ref. 8). Colonies may be quite large, yet workers are seldom seen above ground ... and even those that venture out do not go far from home. These ants don't need to forage. They tend aphids feeding on plant roots and/or they just wait for food to fall tumble in through the funnel.
Late in the day I came across a large funnel with several workers active at the surface. I collected one for identification.
Australia has eight species of these 'funnel ants'. Aphaenogaster barbigula is found in semi-arid parts of eastern Australia ... including north-western Victoria (ref. 8). The arrangement of hairs beneath the head is a clue to the species identity.
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!
The volcano-like appearance is certainly reminiscent of a funnel-ant nest. But there was just this one mound. And the opening was relatively small.
Might this be the home owner (a species of Camponotus I believe)?
These small, shiny black ants were purposefull moving in and out of the nest. So either they are indeed the rightful homeowners, or they are moving in. Another puzzle I didn't have time to solve. Perhaps an accurate species ID will help. Later.
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.
Notoncus are described as general predators, foraging on the ground. These little ants seem a good match, both in behaviour and general appearance.
Ants of this genus are commonly called Sugar Ants or Carpenter Ants ... however, the taxon is so large and diverse, these references to their food preferences and nesting habits don't necessarily apply.
These ants were clearly nesting below ground, rather than inside a piece of wood, so not carpenters at all.
Tiny (<3mm long) and quite slow moving as they carted grains of sand from their nest opening to the small, surrounding mound.
Just one of these sighted.
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).
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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.
she was producing a startlingly blue ootheca!
These green egg cases are a common site in the area. Perhaps they are blue when first produced, or maybe they are from a different mantid species.
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).
male & female ... almost in copula
male, immediately after the female fled the scene
Then there were the myriad other orthopterans and other late-season insects. Species-level identification for some remains a work in progress.
possibly C. tricolor
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