Tomato fly – revisited

An email conversation with an entomologist from New South Wales prompted the addition of a paragraph (in bold) to this article from about a year ago.

I picked a tomato off the bush the other day and noticed a little hole in it. I cut it open and saw that the contents were looking a bit ordinary, as if it was about to rot. Under higher magnification I could see the culprits – fly larvae – yep, maggots! The image below shows a close-up of one.

tomato fly larva

Queensland fruit fly (Bactrocera tryoni) and Mediterranean fruit fly (Ceratitis capitata) are known to lay their eggs in tomatoes, but neither of these species is found in my region of Victoria. The larvae of vinegar fly (Drosophila melanogaster) – known in America as “fruit fly” – feed in fallen rotting fruit, but this tomato was on the plant. So what species of fly produced the larvae?

I put the offending tomato in a plastic container and waited. Over a few days the larvae grew bigger, allowing me to take the photograph above, and started to jump around the container. I knew this was a sign the larvae didn’t want to be in the moist tomato pulp anymore, and were looking for somewhere dry to pupate. I shepherded as many jumping larvae as I could into a dry container with some tissue paper at the bottom, and by the following day they were all pupae.

The flies haven’t emerged yet, but I know what species they are because I went through this same exercise last year. Behold, the metallic-green tomato fly Lamprolonchaea brouniana (Diptera: Lonchaeidae).

metallic green tomato fly

These little flies are only about 4mm long, so they might be a bit hard to see in the garden. The good news is that, in my garden anyway, they are not in very large numbers and don’t lay eggs in every tomato. It is an endemic species that has been most commonly collected from the temperate south. Those wanting to learn more about this pretty little fly could jump onto the Australian Fauna Directory here.

(Note – The “jumping” behaviour of the larvae of these flies is not unique. Queensland fruit fly larvae also “jump” when they leave the larval substrate to pupate. My NSW correspondent suggested that this has led to some confusion in Victoria where people are assuming these metallic-green tomato fly larvae are Queensland fruit fly larvae. Then they wonder why their Queensland fruit fly traps and baits, which are specific to QFF, aren’t working. This illustrates why accurate identification is vital in pest management.)

One more thing about the vinegar flies mentioned above. Don’t be alarmed if you find lots of little flies in your compost. Vinegar fly larvae help with the decomposition process. You don’t need to “get rid of them”! Vinegar flies are about 3.5 mm long and look like this (below).

drosophila

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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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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

Adult male moths have wings but the females are wingless and remain in their cases after they have pupated. Mating and egg laying also takes place within the case. When the eggs hatch the tiny larvae lower themselves on silken threads from the rear end of the case. Larvae begin feeding and building their own cases, and as the larvae grows so does the case. The case moth illustrated below is another species of Lepidoscia. This case is a work of art!

Lepidoscia

Our next master builders are paper wasps of the family Vespidae. Paper wasps are social insects that build multi-celled nests from chewed wood mixed with saliva. Females lay an egg in each cell, and the hatching maggot-like larvae are fed with chewed up insects, usually caterpillars. Adult wasps feed on flower nectar. Nests may be located under tree branches, on rock walls, or unfortunately also under eaves of houses, in carports or on fences where they can be a nuisance. Paper wasps possess powerful stings and some people are highly allergic to their venom. The wasps on the nest below are of the genus Polistes.

Vespidae

It’s only when you take a close look at the inside of a nest that you can see the precision with which these wasps build. It’s hard to believe that this (below) is made from chewed up wood and saliva!

wsp nest

Video of a master builder – Potter wasp building her nest.

 

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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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