Scorpion flies

Mecoptera is a minor insect order with only 27 known species found in Australia. Members of this order are often called ‘scorpionflies’ or ‘scorpion flies’ because males of the family Panorpidae (which doesn’t occur in Australia) have curving genital segments resembling a scorpion sting (below).

male scorpionfly

Males of common Australian species don’t have this ‘scorpion tail’. Australian species are often called ‘hanging flies’ because they hang from plants (and other objects as you can see below) by their forelegs and midlegs. Various species of the genus Harpobittacus, our most common scorpion flies, are found in eastern and southern Australia, including Tasmania and south-west Western Australia. They are often mistaken, especially when flying, for other long-legged insects such as crane flies or large (very large!) mosquitoes.

scorpion fly

Common Australian scorpion flies usually have slender elongated bodies and very long legs, with long narrow wings with a span of up to 50mm. Scorpion flies have a distinct beak and two pairs of wings (unlike true flies of the order Diptera, which have just one pair). Common species of scorpion flies are black and reddish brown, or fully black.

Scorpion flies are predatory and do all their grasping and manipulation with their hind legs. They can catch passing insects with their hind legs, or may actively hunt for prey among plants, sweeping them with their hind legs. They are amazingly dexterous with those gangly legs. The scorpion fly in the image below was particularly deft. It was eating a beetle from one end and then spun the carcass end over end like a football (an AFL football that is), so it could begin feeding from the other end.

scorpion fly feeding

Males give off pheromones to attract females from a distance. To entice a female closer a male offers the female a nuptial meal of an insect he has caught with his gangly hind legs. Females choose males by the size of the offered meal – the male in the image below was certain to mate because he has offered two flies as a meal. Fly nerds will notice that one part of the meal is a species of hover fly (Syrphidae) and the other is a species of blowfly (Calliphoridae). Mating may last up to 10 minutes, but once mating has finished the male flies off, along with his gift, to find another female. Males may mate with as many as 8 females per day.

scorpion flies mating

Once their eggs are fertilised, females drop their eggs on the ground, where the eggs may lie dormant for several months. After hatching, the larvae (which superficially resemble caterpillars) feed on dead insects and plant material and moult through four growth stages. Pupation takes place in a cell in the upper levels of soil. There is only one generation per year.

Scorpion flies may look a bit weird and/or scary to some people, but there is no need to be alarmed – they are useful garden predators. Of course, insect nerds like myself find them endlessly fascinating!

 

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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

Common cuckoo wasp species are noted for laying their eggs in the nests of mud-dauber wasps of the family Sphecidae and potter wasps of the family Vespidae. Some species of cuckoo wasps lay an egg into a mud nest cell while it is still open, and being provisioned by the host wasp. Other cuckoo wasp species chew their way into sealed mud nests to lay eggs.

When cuckoo wasp larvae hatch they may feed on the food stored for the host, or feed on the host larva, depending on the species of cuckoo wasp involved. Here is some terminology for you: if the cuckoo wasp larva feeds on and kills the host it is termed a parasitoid, but if it feeds on the host’s provisions it is known as a cleptoparasite. Either way the host larva dies.

Host wasps are armed with powerful jaws and stings, so cuckoo wasps try to enter nests when the host wasps are off gathering nest provisions. But they have evolved some defences if they are caught in the act. Cuckoo wasps have a very thick exoskeleton and they roll themselves into a ball and tuck their legs in to avoid damage.

Chrysididae

I see blue-banded bees (Amegilla sp.) almost daily in the garden at my place in western Victoria. I enjoy their noisy buzzing and I know they are excellent pollinators. Unbeknownst to the blue-banded bees there is another species of bee, the cuckoo bee Thyreus sp. (below), which follows them and lays eggs in their nests. The cuckoo bee is a cleptoparasite. When its egg hatches inside the blue-banded bee nest the larva eats all the nectar/pollen provisions placed there by the blue-banded bee. When the blue-banded bee larva hatches from its egg, there is no food left and it dies.

Thyreus sp.

There is one more group of usurpers worth mentioning and that is the parasitic wasps Gasteruption spp. (gasteruptids) of the family Gasteruptiidae. This slender wasp (below) lays eggs in the nests of several groups of native bees. This wasp is a parasitoid and a cleptoparasite – its hatching larvae feed on the eggs or larvae of the host bees and then the pollen store. It is particularly worrisome for people who keep bee homes/insect hotels – constructions that are now de rigueur in domestic horticulture. Gasteruption has an egg laying apparatus (ovipositor) longer than its body that can penetrate the tunnels and nests of native bees. This slender wasp is easily recognisable and may be seen hovering near flowers like a Will-o’-the-Wisp.

Gasteruption

None of these parasitoids and cleptoparasites, be they cuckoo wasps sneaking up on mud wasp nests, or cuckoo bees tracking blue-banded bees, or wispy gasteruptids penetrating native bee nests, ever wipe out their hosts. It would be counter-productive for a parasitoid or a cleptoparasite to do so because that would mean their own death. As long as there is a balance all will be well – complicated certainly – but okay. The insect world, particularly the wasp world, is a very complex one.

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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?

I recently found a small colony of an introduced cottony soft scale which has the tongue-twisting scientific name Pulvinariella mesembryanthemi (image below). Thankfully it has a couple of more easily  pronounced common names ‘iceplant scale’ and ‘cottony pigface scale’. ‘Iceplants’ and ‘pigface’ are succulent plants within the botanical family Aizoaceae – one genus of this family is Mesembryanthemum.

iceplant scaleThe female insect (the brown disc) is about 3 mm in diameter and the cottony ovisac is about 4 mm long. Females may lay as many as 2,000 eggs each during their short life of a few weeks. Males are rare in these scale insects, in fact they are not required because the females can reproduce parthenogenetically. The image below shows an open ovisac of one the cottony scale insects revealing the eggs inside. That’s a lot of eggs!

insect eggsMobile nymphs known as ‘crawlers’ hatch from the eggs and move away from the adult female to a different part of the plant, or further afield. People often ask me how immobile scale insects can spread from one plant to another – well, this is how. Crawlers may wander from one plant to another using their own six legs, or they may hitch a ride on an air current and travel effortlessly over much greater distances. The animation below shows a crawler emerging from under its ovisac while I was shooting images for a focus stack. Can you see it?

Insect animation

Crawlers eventually settle on a plant somewhere and moult into sessile (immobile) nymphs which plug into the sap flow of the plant with their sap-sucking mouthparts, then moult into a larger nymph, and then moult once more into an adult. And so the cycle goes.

There is one more cottony scale insect which I should mention. That is the cottony cushion scale Icerya purchasi now classified in the family Monophlebidae. This native Australian insect was accidentally introduced into the United States in the 1860’s and within a couple of decades brought the US citrus industry to its knees. I reckon that sounds like a good topic for a future one minute bugs.

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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

Trictena atripalpis has the highest recorded egg laying capacity among non-social insects. One female was reported to lay 29,100 eggs, and when dissected 15,000 fully developed eggs were found in her ovaries. That means she had the potential to lay over 44,000 eggs. A female ghost moth lays her eggs singly while flying, ‘bombing’ them in the general direction of the roots of gum trees. The more eggs she lays during her short life the more chance there is that some hatching larvae will survive to find food and start a new generation. (Social insects such as ants, bees and termites beat that egg laying record hands down – e.g. queen driver ants can lay a couple of million eggs every month.)

The larvae (below) of these moths live under the soil in tunnels and feed on the roots of various species of gum trees. They pupate under the ground in their tunnels and the mobile pupae wriggle towards the surface waiting for rain.

hepialid larva

‘Rain moth’ is a great name for this moth because the adults only emerge from their pupal tunnels in autumn after heavy rain or when rain is imminent. The moths are easy to find as they are attracted to our house lights at night and some years they almost cover the wall. There are often one or two individuals who ‘jump the gun’ and when I see these early moths I know there is rain on the way. After emergence their pupal cases (below) are left protruding from the ground, sometimes mistaken by some people for cicada skins.

hepialid pupa

The ghost moths which visit us are a vital part of our local web of life, where for every creature there is another creature which will try to eat it. Ghost moth larvae are reasonably safe in their underground tunnels but emerging moths are vulnerable to attack. I will never forget the night I watched ghost moths landing on our window screens only to be systematically snatched off by insectivorous bats. Tawny frogmouths also like to eat them. The owls make quite a noise as they crash into our windows while catching the moths!

The rainforests of Australia are home to beautiful ghost moths of the genus Aenetus, commonly known as ‘splendid ghost moths’. The spectacular Aenetus mirabilis is found in northern Queensland and has a pale blue male and a green female. We have some beautiful species where we live too, such as Abantiades hyalinatus pictured below.

ghost moth

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Mantis-fly image wins award

An image of mine (below) won the Image Laurel at the 2016 Horticultural Media Association Australia last night. You can read more about this insect here.

mantis-flyThe award I won looks like this:

Image Laurel

The citation from the judges was: “Denis Crawford’s Mantis-fly image has superb resolution of detail revealing a technical mastery of close-up nature photography. The result is a crystal clear depiction of the Mantis-fly that brings the insect to life.”

Below is a short video of my acceptance speech:

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I love parasitoids

To most people the word “parasite” conjures up all sorts of images from tapeworms to brain-eating amoebas to scenes from the film Alien. So a “parasitic wasp” must be something really freaky and horrible then? To us – no; but to an aphid or a caterpillar or some other target insect – yes.

Technically a parasitic wasp isn’t a parasite at all. True parasites like tapeworms don’t normally kill their hosts, because that would mean their own death. So insects such as parasitic wasps and flies which parasitise and kill other insects are known as parasitoids.

parasitoid Continue reading I love parasitoids

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