Black Slugs & Bondi Trams

It’s early autumn here in the Grampians in western Victoria which means that it is peak time for some of my favourite caterpillars – cup moth larvae.

Cup moths are found across Australia, and they are members of the moth family Limacodidae. The common name ‘cup moth’ is derived from their cup-like pupae (pictured below). There are more than 100 species found in Australia, in about 25 genera. Larvae have varying tastes depending on the genus involved.

Moth cocoon

The cup moth larvae I find here are in the genus Doratifera and I have only ever seen them feeding on the leaves of Eucalyptus species (although they have been recorded on other plants). The most common species here are the black slug cup moth (Doratifera casta), and the four-spotted cup moth (Doratifera quadriguttata).

There are usually two generations of cup moths per year with numbers of larvae peaking in autumn (now!) and spring. The adult moths are small, nondescript, mottled brown moths with wingspans of about 30 mm. An adult black slug cup moth (Doratifera casta) is pictured below.

Limacodidae moth

Female moths lay their eggs in clusters covered with a dense mat of special scales from the posterior end of the female moth’s abdomen. This covering of scales protects the eggs from desiccation and predators.

When the larvae first hatch from their egg mass, the first couple of instars are gregarious and feed together on a single leaf, eventually skeletonising it. It is only when the larvae grow larger that they separate, and consume whole leaves by themselves, usually only leaving the mid-vein.

Where on earth does that common name black slug cup moth come from? My much thumbed copy of Moths of Australia by the legendary lepidopterist I.F.B. Common reveals “the larvae are slug-like and are the only external-feeding moth larvae that lack abdominal prolegs ….. thoracic legs are usually reduced in size”. Limacodids in North America are generally referred to as ‘slug moths’, but Doratifera casta is the only one lucky enough to endure that title here. I think they are quite nice myself – here’s one in close-up (below).

Doratifera casta

The larvae of other Doratifera species are much more brightly coloured than D. casta, including my other local species D. quadriguttata (pictured below). What they, and other species, have in common are the rosettes of stinging setae (spines) that expand when the larvae are disturbed. You can clearly see four sets of raised setae in the image below.  I.F.B. Common says “they are capable of inflicting a sharp stinging sensation rather like that of nettles”.

Doratifera quadriguttata

There is one other species that I should mention and that is the mottled cup moth (Doratifera vulnerans), the larvae of which are sometimes known as ‘Bondi trams’. These brightly coloured larvae have eight sets of stinging setae – four at each end. I spent ages getting the image below. I tried to provoke it onto raising those stinging setae by poking it with a pencil which had no effect at all! It was only when I gripped it with some forceps that it reacted – perhaps it thought it was about to be eaten by a bird?

Doratifera vulnerans larva

I plan to shoot a video over the next week so you can see some cup moth larvae in action. Stay tuned!

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The Flies of March

Most Australians are very familiar with the insects known as March flies. In temperate Australian zones these flies are commonly encountered over the warmer months of the year, and are unwelcome guests on many camping holidays! Tropical species may occur at any time of the year. In other words March flies don’t appear exclusively during the month of March.

Tabanidae

Perhaps the common name stems from the March flies of the northern hemisphere which may arrive during the northern spring (i.e. around March). Unfortunately those northern hemisphere March flies are in a different family (Bibionidae). I include a picture of an Australian bibionid fly (Dilophus sp.) below. As you can see it doesn’t look anything like an Australian March fly. The March flies we know are members of the family Tabanidae, and we have about 400 species of tabanid flies here in Australia.

Bibionidae

Australian March flies are notorious for their painful bite, and some species are pests of livestock which gives rise to another common name for them – ‘horse flies‘. Male March flies don’t bite, they feed on nectar. It’s only the females that feed on blood, they need the protein to lay fertile eggs. There are some March flies (both male and female) that never feed on blood – they only feed on nectar. The beautiful Scaptia auriflua is one of those – just click this link to learn more about those.

Tabanidae

Hows that for a proboscis (above)? No wonder it hurts. Female March flies puncture the skin with the spike you can see at the tip of the proboscis, and then mop up the blood with spongy mouthparts. They don’t suck blood like mosquitoes do. March flies tend to be fairly slow, especially when they have landed on your skin for a blood meal. They do a fair bit of investigating of the skin before inserting their spike, and are easily swatted away.

The larvae of common March fly species usually occur in damp soil, vegetation in swamps, and in river mud, where they prey on other insects. Adult March flies are themselves preyed on by other insects such as robber flies, reptiles such as skinks, and birds. They may be annoying to us (and in the case of some overseas species spread diseases) but they are part of the environment we live in. This post was inspired by the beautiful March fly below (I’m not sure of the species) that I found in my vegetable garden just the other day.

Tabanidae

 

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Cottony scales

This post was originally published in May 2016. Since then it has clocked up a very surprising 8750 hits! I wonder what makes it so popular? I am republishing the post (with minor edits) for those that missed it the first time.

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 the ovisac. Can you see it? This wasn’t a planned shot of the crawler – it happened by chance as I was shooting a series of images for a focus stack.

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 will write more on this topic in a future one minute bugs.

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