What’s good about ants? Plenty.

Many people, especially gardeners, only see ants as pests, but they couldn’t be further from the truth. These days I work weekends in a garden centre, and when summer arrived every second customer I encountered wanted a product to kill ants. One person even asked me for the “Agent Orange” of ant insecticides! They were somewhat bemused when I asked “What sort of ants are they, and why do you want to kill them?”

ponerine ant
This harmless ponerine ant is holding a water drop in its mandibles.

There are more than 1,300 described species of ants in Australia, but only a minority are considered to be pests. Most ant species are beneficial in some way. Ants are extremely important in the environment and are sometimes referred to as ‘ecosystem engineers’. For example, in bushland, ants are vital dispersers of seeds, a mutually beneficial practice known as myrmecochory. Many Australian plants, about 1500 species or so, have evolved to produce seeds with elaiosomes, which are expendable seed parts containing oil, protein, starch, sugar and vitamins. Ants collect the seeds, and carry them off to their nests underground. However, they only eat the elaiosomes and discard the rest of the seed in a ‘rubbish tip’ section of the nest, or hide them under leaf litter outside the nest. The seeds are then sort of planted, safe from predation or fire, where they can germinate safely.

Mind-boggle alert! Some stick insects exploit these ants’ seed-burying behaviour by laying eggs that look like seeds (see below), and even have an expendable fatty part for the ants to feed on. The eggs are collected by ants and taken into their nests where they are safe from predators. When the young stick insects (nymphs) hatch they even look and smell like ants. The nymphs then wander out of the nest, past the unsuspecting ants, and up the nearest gum tree to feed on the leaves.

Phasmid eggs

Anyway back to the ants. Ground-dwelling ants aerate the soil while digging their nests, which allows water to penetrate the soil more effectively. Those ants that make their nests in dead wood aid the decomposition process of that wood. Many ant species are predators or scavengers consuming vast numbers of the eggs, larvae and adults of insects and other invertebrates − either dead or alive. Ants in turn are food for many creatures such as birds, echidnas, reptiles and other invertebrates.

Some common ant species that are predators and scavengers include funnel ants (Aphaenogaster spp.), green tree ants (Oecophylla smaragdina), meat ants (Iridomyrmex spp.) and sugar ants (Camponotus spp. – pictured below). These ants should be encouraged and respected rather than bombed with insecticides.

camponotus

Where I live in Western Victoria there is really only one ant species to be wary of and that is the Jumping Jack ant (Myrmecia pilosula) pictured below – aka Jack jumper, hopper ant, skipper ant. Jumping Jack ant stings can cause anaphylaxis, a life-threatening condition in some people typified by constriction of the throat and difficulty in breathing. Milder symptoms include swelling and itchiness around the wound. They are extremely aggressive ants by nature and move in a characteristically jerky, jumping manner. Their movement may look a little comical, but there is nothing funny about the sting!

jack jumper ant

In a future blog post I will be writing about how some butterflies have interesting associations with certain ant species. In some cases the butterflies are totally reliant on the ants for their survival.

 

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Insect Architects

After a few months off for house painting one minute bugs is back!

I was prompted to write this post after completing an article for Hort Journal Australia on a similar topic. My argument in the Hort Journal piece was that insects are not mathematical or engineering geniuses, and that their behaviour is dictated by the instincts they have evolved with. All very scientific and anti-anthropomorphic. The post here is a bit different. Let’s marvel at the exquisite perfection of some of the structures that insects build.

Our first architects are moths of the family Psychidae – the case moths. These are harmless creatures found in most gardens throughout Australia. Cases are spun by caterpillars from silk to which twigs, sand, moss, lichen, leaves or bark are attached. The cases can open and close at each end, the front end for feeding and the rear end for ejecting droppings. I believe the species illustrated below is Lepidoscia arctiella – look at how precise those little bits of twig are!

Psychidae

Continue reading Insect Architects

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Cuckoos & cleptos

Most of us are familiar with the activities of avian cuckoos where a bird lays its eggs in the nest of a host bird of a different species, after kicking out the eggs that were laid by the host. We have a dozen or so species of cuckoos in Australia and some of them utilise the nests of birds half their size. The worst mismatch I have seen was a pair of exhausted Superb Blue Wrens (Malurus cyaneus) trying to feed a massive fledgling Fan-tailed cuckoo (Cuculua pyrrhophanus). The young cuckoo was never happy with the amount of food brought to it and constantly pecked its foster parents.

Did you know there are insect cuckoos too? Granted there’s not a lot of the bullying going on like in the bird example described above, but there is certainly similar amounts of clandestine behaviour. There are about 75 species in the wasp family Chrysididae in Australia, with common species being referred to as “cuckoo wasps”. They vary in length from about 6 mm to 22 mm in length and they are strikingly beautiful insects because of their metallic colours.

Chrysididae Continue reading Cuckoos & cleptos

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Cottony scales

There are about 80 species of ‘soft scale’ insects of the family Coccidae found in Australia. The ones I find most interesting are the pulvinariine soft scales which are known colloquially as ‘cottony scales’, ‘cottony soft scales’ and (my favourite) ‘cushion bears’. These common names help to describe the cottony egg sacs (ovisacs) of adult female scales. The image below shows adult female Pulvinaria dodonaeae on the leaves of a species of Myoporum.

Cottony soft scaleThe insect itself is brown in colour and the ovisac is the furrowed white mass behind. Pulvinaria dodonaeae is endemic to Australia and is not considered to be a pest. Its species name, dodonaeae, coveniently indicates some of its host plants are within the plant genus Dodonaea. One of the exotic (i.e introduced from elsewhere) cottony soft scales found in Australia goes by the name of Pulvinaria hydrangeae. Can you guess which plant it occurs on? Continue reading Cottony scales

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Night of the ghosts

Ghost moths are members of the moth family Hepialidae and there are about 150 species found in Australia. The common name “ghost moth” comes from a European species whose white ghostly males are seen hovering over open ground in a conspicuous display flight to attract females.

We have several ghost moth species at our place in the Grampians and the largest (15 cm wingspan) and most numerous is Trictena atripalpis (below). Common across the southern half of Australia, this moth and a couple of related species are known under common names such as ‘bardee’ or ‘bardi’ grub, rain moth, swift moth or ‘Waikerie’. Little wonder that entomologists use scientific names when referring to particular insects! The moths only live for one day – their only role in life is to mate and, if female, to lay eggs. The moths don’t feed or drink because they don’t have the appropriate mouth parts to do so.

hepialid moths Continue reading Night of the ghosts

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