Preying on a mantis

For every insect out there, there is another insect which will try to eat it or breed in or on it.

Praying mantids are common predatory insects found in virtually any part of Australia in any habitat where they can find prey. Mantids are an insect Order all of their own known as Mantodea, comprising about 2,500 species worldwide, and about 200 Australian species. These insects are commonly called ‘mantises’ or singularly as a ‘mantis’ – but they are more correctly known as ‘mantids’ or singularly as a ‘mantid’.

Mantids are instantly recognisable insects with their triangular heads and their characteristic way of standing with forelegs held together as if they were praying – hence ‘praying’ mantid (image below). The word ‘mantis’ is derived from the Greek word for ‘seer’ or ‘prophet’, which probably alludes to their praying stance. There is a genus of mantids bearing the name Mantis – for example the classic ‘praying mantis’ Mantis religiosa found through Europe, Asia and Africa. Australia only has one representative of that genus, a mantid known as Mantis octospilota.

Praying mantid

Mantids can be found from treetops to ground level usually widely dispersed and solitary. They are non-specific predators and will prey upon a wide range of other insects, and some large species have been observed feeding on frogs and small lizards. Mantids will attack and eat their own kind – which is probably why they are mostly solitary! Female mantids are known to eat males after, and sometimes during, mating. Serious entomological texts maintain that this activity is usually observed under caged conditions and rarely in the wild. Courtship usually doesn’t precede mating; males just tend to leap onto the backs of females at opportune moments.

The triangular heads of mantids are very mobile and they have large eyes, which must help enormously when spotting prey . Mantid forelegs are armed with rows of spines (described taxonomically as ‘raptorial’). When prey is within reach, the forelegs are shot forward and the victim is impaled and held tight with the spines, and then lifted up to the mantids mouth parts and eaten alive.

Some species sway from side to side while slowly stalking prey – possibly mimicking a twig swaying in the wind. Interestingly other insects such as certain species of katydids also sway like leaves in the wind, not to stalk prey but as protection from predators. Most mantid species rely on cryptic colouring as camouflage and sit motionless, waiting for prey to come to them. The bark mantid Gyromantis sp. (image below) is a classic example.

Praying mantis

Males of most species have two pairs of wings, both of which are used in flight, while females of most Australian species have either reduced wings or no wings at all.  A males of a large species in flight is a sight to behold. The forewings of winged species are hardened to protect the more delicate hind (flight) wings. Mantid species vary in size from about 10 mm to a massive 120 mm in body length. Common species such as the garden mantid Orthodera ministralis (image below) are about 40 to 50 mm in length.

Praying mantis

Mantid eggs are laid in moist frothy liquid which hardens into an egg case (ootheca). Egg cases and are commonly found on fences and tree branches, and may contain hundreds of eggs. The size and shape of the egg case, and the number of eggs within, varies from one species to another. The eggs hatch into nymphs (essentially miniature versions of their parents without wings) which immediately hunt for and feed on small, soft bodies insects. The eggs of mantids are often parasitised by parasitic wasps and flies, and eaten by predatory insects such as ants, as well as by small mammals and birds.

I kept a mantid egg case in a container to see what would hatch out. About 100 mantid nymphs emerged along with 50 or so parasitic wasps (Podagrion sp.), which lay their eggs in the egg cases of mantids. As you can see from the photograph here (image below) this species of female parasitic wasp has a long ovipositor, but she must insert it in a mantid egg case before it hardens. To achieve this she either follows the mantid female or hitches a ride (a behaviour known in zoology as phoresy). As soon as the mantid egg case is complete, she inserts her eggs inside. The wasp eggs hatch and the emerging wasp grubs feed on the mantid eggs within the protection of the mantid egg case. In the mantid case I collected many mantids survived these clever wasps and hatched before being eaten.

Podagrion

Mantids are usually seen as being ‘good bugs’ but because mantids are usually widely dispersed they have little economic significance. Being non-specific predators they will attack beneficial insects as well as pest insects – unlike us they make no distinction between a pest fruit fly and a beneficial hover fly. However due to their low numbers they are unlikely to significantly affect populations of beneficials. My personal view is they should be seen as ‘benign’ i.e. neither good nor bad – and they are certainly interesting!

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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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Revenge of the Mummy

Have you noticed swollen bronze-coloured aphids on your plants? These are aphid ‘mummies’ caused by the parasitic wasp Aphidius of the wasp family Braconidae. There are several species of Aphidius which have been released in Australia. A species that has established well and is common in urban gardens is Aphidius rosae, a successful parasite of the rose aphid Macrosiphum rosae.

Aphidius wasps are shiny black, slender insects about 3 mm in length with long antennae. The diminutive size of these wasps makes it hard to see them in gardens, but you will see the results of their life cycle within aphids. Adult female wasps lay their eggs singly inside adult aphids and aphid nymphs. To accomplish this a female wasp must bend her abdomen under her legs and inject an egg into the aphid with her ovipositor (‘stinger’). If you were watching and you blinked, you would miss it, as this operation takes less than a second. Obviously I don’t have many images like this one.

Aphidius Continue reading Revenge of the Mummy

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