Historic weevil

I first published this story back in April 2015. Recently, I spoke about this weevil on ABC Radio Ballarat and also at a talk I gave to Friends of the Grampians Gariwerd (FOGG) so I thought now is a good time to republish.

I found this fellow trundling along the road when I went for my morning walk the other day. This insect is commonly known as a Botany Bay weevil (Chrysolopus spectabilis) or by its other common name “diamond weevil”. This is the male of the species. Females are larger insects, making males the lesser of two weevils (sorry, I couldn’t resist!).

Botany Bay weevilBotany Bay weevils belong to an historic group of insects. This weevil was collected by Sir Joseph Banks on Captain James Cook’s voyage to Australia in 1770. Actually we don’t know that Banks himself collected it – it could have been one of his men, or the Swedish naturalist Daniel Solander who accompanied Banks on the voyage. On his return, Banks gave the task of cataloguing his insect collection to the Danish insect taxonomist Johann Fabricius. The weevil was described in 1775, making it one of the first (if not the first) Australian insects described to western science.

Sydneysiders may be surprised to learn that the Botany Bay weevil is not only found around Sydney, but from coastal far north Queensland to eastern South Australia. The weevil is certainly common in New South Wales and its common name probably dates back to the early colonial days of Botany Bay.

To this day we don’t actually know where Banks’ specimen was collected. Was the weevil collected at Botany Bay in April 1770, or during July/August 1770 when Cook was repairing the Endeavour near present day Cooktown, or at one of the other landing points in between? The label on the specimen simply says “nova Hollandia”.

Botany bay weevil femaleBotany Bay weevils are associated with about 30 species of Acacia. Female weevils chew holes in stems at or below ground level in which they lay their eggs. Upon hatching the larvae bore into the stem and usually down into the roots. Adult weevils emerge in the summer, and what spectacular insects they are with their rich metallic green or blue markings on a black background. The adult weevils also feed on Acacia spp. in their characteristic manner of removing the leading shoots several centimetres down the stem.

The Botany Bay weevil has a distinctive defence mechanism. One day I was taking some close-up images of weevils on Acacia provincialis when I got just a bit too close for comfort. The weevil suddenly went stiff, toppled backwards and fell to the ground like an actor in a B grade Western movie. The trick I learned was to move closer to them slowly, taking photos as I went, so they got used to me and the noise of the camera.

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Sap-suckers & sooty mould

Sooty mould is not a plant disease as such but various species of fungi, which grow on the sticky honeydew excreted by many species of sap-sucking insects. A very thick mould layer on leaves may cause a reduction in photosynthesis in plants, which can result in leaves falling prematurely. The main concern to gardeners (apart from the sap-sucking pests which caused it) is that a thick covering of sooty mould on a plant’s leaves is downright ugly.

Sooty mould is a serious problem for the horticultural industry. Ugly plants are unsaleable. Similarly in the citrus industry, the main economic damage caused by mealybugs is by the downgrading of fruit quality due to sooty mould growing on mealybug honeydew. The picture below shows a leaf infested by soft scale insects and the sooty mould they cause – pretty ugly eh?

Sooty mold

Insects which produce honeydew include planthoppers, leafhoppers, treehoppers, psyllids, whiteflies, aphids, scale insects and mealybugs – all ‘true bugs’ in the insect Order Hemiptera. These bugs consume vast quantities of watery sap from which they extract the nutrients they require, particularly nutrients containing nitrogen. Many kinds of sugars are also present in plant sap in abundance, which are not required by the insects and are excreted in solution as honeydew. Almost all the dry weight of honeydew is in the form of sugars. It’s worth tasting honeydew to experience just how sugary it is.

Many bugs propel the honeydew away from them so they don’t become trapped in the sticky stuff as it dries. The honeydew falls to foliage below, often in vast amounts when the insect colony is large. Wherever the honey dew falls sooty moulds may grow. The hibiscus leaf covered in sooty mould pictured below was directly below a leaf (underside) covered in greenhouse whitefly (Trialeurodes vaporariorum).

hibiscus sooty mold

But not all bugs throw their honeydew away. Some psyllids allow their honeydew to harden into protective ‘lerps’ (you can read more about them here) while other sap-sucking insects use honeydew to attract ants which act as their bodyguards. Such interaction between bugs and ants is known as trophobiosis and is based on reward (sweet honeydew) for services rendered (protection from predators). The relationship can be specific and involve a single ant species and a single bug species, or one ant species may interact with several species of bugs, or vice versa.

You don’t have to look far to find ants protecting honeydew producing bugs such as aphids, planthoppers and scale insects  – almost any park, garden, orchard or nursery will be harbouring such a relationship somewhere. The picture below shows some ants attending soft brown scale, and you can even see a drop of honey dew.

Anst feeding on honeydew

If ants are efficient at protecting the pest insects from predation such that pest numbers increase, ant control might be something you consider. For example, organic growers of citrus and other fruit have to use ant control as a means of controlling scale insects and other pests on their trees. To put it another way, controlling the ants gives predators and parasites a chance to control the pest insects. Ant control is simple – you can prevent the ants climbing a tree by banding the tree trunk with horticultural glue or some other sticky substance.

There are no fungicides registered against sooty mould – you must control the insect pests which produce the sticky honeydew on which the fungus grows. The fungus will stop growing once the honeydew source is removed, and will eventually dry out and fall off leaves, or it can be hosed off.

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It’s got 6 legs but it’s not an insect!

Q. When is an animal with six legs not an insect? A. When it’s an entognathous hexapod.

Until fairly recently it was thought that all animals with six legs were insects. It is now widely accepted that there are two classes of six-legged animals – the insects (class Insecta) and the entognathous hexapods (class Entognatha).

The Entognatha are six-legged animals characterized by mouthparts which are hidden away in a pouch in their head (entognathous). The insects (Insecta) have mouthparts which are not hidden (ectognathous).

HEXAPOD Noun. (Greek, hex = six + pous = foot.) Any 6-legged arthropod.
ENTOGNATHOUS Adj. (Greek, entos = within, inner + gnathos = jaw + Latin, –osus = with property of.) Hexapods with mouthparts recessed within head.
ECTOGNATHOUS Adj. (Greek, ektos = outside + gnathos = jaw + Latin, –osus = with property of.) An organism with protruding mouthparts.

The class Entognatha contains three orders: Collembola (springtails), Protura and Diplura. As well as recessed mouthparts these three orders have a few other things in common. They are all wingless (apterous). Also there is no visible change in form between the life cycle stages other than in size, meaning they don’t go through a process of metamorphosis and so are termed ‘ametabolous’.

The largest of these orders is Collembola, the springtails. There may be as many as 2000 species in Australia, many of them undescribed. They are called springtails because they have a prong at the tip of their abdomen (known as a furca) that is folded back like a spring. When released, the individual is launched into the air. You can see the furca in the image below. Springtails are usually tiny animals about 1mm to 3 mm long.

Collembola

Almost all springtails are considered beneficial species because they contribute to the breakdown of organic matter. There is one pest species in Australia and that is the so-called lucerne flea (Sminthuris viridis) which may damage emerging seedlings. Springtails don’t have eyes as such, instead they have a cluster of light sensing organs (known as ocelli) on each side of the head. You can see ocelli on the side of the head of the super cute springtail in the image below.

Springtail

Protura are rarely seen, tiny (< 2 mm long), pale, hexapods which may occur in soil, leaf litter, decaying wood and moss. There are about 30 described species in Australia. They have no eyes or antennae and hold their front legs forward apparently to feel their way around. Proturans were not described until 1907 and to this day very little is known about their behaviour. Some species have been observed feeding on mycorrhizal fungi, but it remains to be seen if all Proturans feed exclusively on mycorrhizal fungi. The line drawing below comes from CSIRO.

Protura

There are 31 described species in the order Diplura which occur in Australia. They vary greatly in form and size from pale delicate hexapods less than 5 mm in length to robust earwig-like species which may reach 50 mm in length. Diplurans have no eyes but do have a pair of antennae. They also have a pair of abdominal appendages known as cerci which are filamentous in the families Campodeidae and Projapygidae, but pincer-like in the families Japygidae, Heterojapygidae and Parajapygidae.

Diplurans of the families Campodeidae and Parajapygidae appear to be herbivorous, Projapygidae may be omnivorous, while the rest appear to be carnivorous. Heterojapyx (picture below) is certainly carnivorous. It waits buried in soil with only its pincers (forceps) above the surface, ready to grab any unsuspecting prey wandering by. Superficially it may resemble an earwig, but the lack of eyes and wings gives it away. I had never seen one of these in the flesh until recently when I stumbled upon one while chopping wood on my property. What a find!

Heterojapyx

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The Rain Moths are back!

I see them every year and they never fail to intrigue and excite me. We have several species of moths in the family Hepialidae which visit our property, but by far the most numerous and most spectacular is the species Trictena atripalpis.

Trictena atripalpis

They usually all emerge on the same night and are drawn to our house lights, as you can see above.They need to emerge together because they only live for one night, so they must find a mate and the females must lay their eggs on the night. The trigger for their emergence is heavy rain, and we had quite a dump last night, about 40 mm or so.

In the morning there were only a few survivors left. During the night they were systematically picked off by owls and bats, and in the morning the day birds got the rest. I was only able to find two surviving moths around the house in the morning. The image below shows one of them. It should give you a pretty good idea of their size!

Trctena atripalpis

These moths emerge from underground, because their larvae are root feeders, leaving a pupal skin poking out of the ground. Sometimes just the tip of the skin is poking out of the ground, like in the image below, but on other occasions the entire skin is accidentally hauled out onto the surface.

pupal skin

If you are interested in learning more about these moths you can read one of my earlier posts entitled “Night of the Ghosts“. There is also a page on these moths in “Backyard Insects“.

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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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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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