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World Wide Web II

June 1, 2020
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This is probably the first blog since we started in 2011 that has not featured a photo of a critter. But you can certainly see where they have been. If you have been cycling or walking recently you would have felt it. Or if you have been driving when the sun is just at the right (correct) angle you maybe would have seen it – silk streamers festooned on everything. Not just one or two but thousands, dare I say millions of them (pictured left). One of the sources of this phenomenon is spiders.  A previous blog (Keeping the wolves from your door) featured Wolf Spiders and mentioned that the young spiderlings disperse by releasing a strand of silk into the breeze and ‘ballooning’ away. Now is that time.

Recent studies have shown that simply releasing a silk strand into the breeze does not provide the required lift to float the spider away. Spiders use the earth’s electric field to get the required lift. When released the silk strand picks up a negative charge, the same as the surface on which the spider is sitting. This creates a repulsive force. In addition the air is positively charged. Spiders can detect these electric fields using sensitive hairs on their bodies and the electrical repulsive and attractive forces assist them to get airborne on their silk streamer. It is an effective way to disperse. Spiders have been found many kilometres in the air, and thousands of kilometres out to sea.

In these times of restricted air travel and climate change denial, the invertebrate world seems little fazed and is travelling using renewable energy.

Rose Hillers

May 27, 2020

Crimson Rosellas are a dime a dozen at our place – permanent residents that have been recorded, usually in quite large numbers, for every month of the twenty years that we have been keeping records. Not so their close cousins Eastern Rosellas, which although fairly common usually make only a fleeting appearance and are much more wary. So it has been pleasing that recently a group of four Easterns has been regularly spotted here on our COVID-19 lock-down walks.

The Eastern Rosella is the “original” rosella, whose name has an interesting back story. They were a common sight to the early colonists (or invaders, depending on your viewpoint) around Rose Hill (now Parramatta) west of Sydney. So they became known as Rose Hill Parrots, shortened to Rose Hillers and subsequently Roselle and eventually Rosella, by which sole name it was known for some years – the Crimson Rosella in those days being known as Crimson Parrot among several other early names. [Ref. Ian Fraser and Jeannie Gray, Australian Bird Names (2013)]

Other early names for the Eastern Rosella included Rosehill Parrakeet, Common Rosella, Rosy, Red-headed or White-cheeked Rosella and Nonpareil Parrot, aptly describing as “unequalled” the bird’s amazingly coloured plumage.

Due to their continual wariness, the few photos we managed to take have been front-on and fail to show the wonderful contrasting patterns on the back of the bird, which can be seen on the photo at right taken by David Francis, NatureShare.

Every toadstool’s a stage

May 20, 2020

For Fungus Flies (Tapeigaster sp.), pictured left, all of life’s dramas are carried out on the surface of a mushroom. The mushroom represents a combat zone, boudoir and nursery. The wet start to autumn means there are mushrooms a-plenty and hence heaps of drama for the flies. Australia has dozens of native Fungus Fly species and several introduced ones. They all live in the cool temperature south east of the continent.

For the males in Fungus Fly world the chances of mating depend on the attractiveness of the mushroom you ‘own’. A male fly will patrol the perimeter of its mushroom to ward off any male intruders. Ownership disputes are settled by a boxing match. Each male will raise its front pair of legs and ‘box’ the other until one of the combatants gives up and flies away.

If the male is successful in attracting a female mating occurs on the mushroom and soon after the female fly lays eggs (pictured above right) in the mushroom. The resulting larvae rapidly consume the mushroom leaving it as a heap of ooze in a matter of days.

There is a twist to the tale however. Like all flies, after mating the male and female fly off leaving the young to fend for themselves. This leaves the maggots vulnerable to predation if they venture too close to the surface of the mushroom. Pictured below is an ant carrying off a Fungus Fly maggot for dinner, either for itself or its young.


It’s life and death drama on the mushroom stage.

World-wide web

May 18, 2020

For most people the stereotypical spider web is the flat wheel-like structure seen suspended between bushes or on fences (pictured left). These are constructed by a group of spiders known as Orb-weavers, in English the word ‘orb’ infers ‘roundness’. These spiders are found all over the world. As with any large group of fauna there are no strict rules – not all orb-weavers build orb-shaped webs and there are some spiders that are not orb-weavers that do build orb webs (it’s not the web that defines the spider!).

 

The orb-weaver builds the web by floating silk in the wind from one point to another. From the middle of that strand it repeats the process. These strands radiating from the centre are not sticky and the spider uses these to navigate around the completed web. Once the radial structure is completed the spider walks around the web laying concentric circles of ‘sticky’ silk with which it catches prey. Many such spiders are nocturnal. During the day orb-weavers will sit camouflaged in the vegetation (see photo below). At dusk they will consume or dismantle the existing web and build a new one for the night.

Lynx Spider 1 DSCN7811

Slender Leaf-shaped Orb-weaver (Araneus talipedatus)

 

Like all spiders orb-weavers have eights eyes distributed as two rows of four, one row above the other. For orb-weavers the middle two eyes of both rows form a tight square configuration with the outer eyes being spaced further apart.

Orb-weavers exhibit a large variety of shapes, sizes and colours. In suburb gardens, Golden Orb-weavers (Nephila sp.), pictured right, are commonly seen orb-weavers. Those who go bushwalking during summer will be familiar with the webs of Spiny Orb-weavers such as the Australian Christmas Jewel Spider (Austracantha minax), below, which appear to cover every bush.

Orb-weaver webs are usually vertical and the spider sits with its head facing down. The male is much smaller than the female and mating is initiated by the male tapping the web to signify its presence – the arachnid form of Tinder!

The Robin Routine

May 15, 2020

Some fauna like humans are creatures of habit. On my daily cycling trips I know what birds will be in what areas because in the right season they come back to the same spot. At the moment the robins are coming down from the highlands to winter in the district. It is a sure sign, if my fingers numbed with cold didn’t remind me, that winter is approaching. And every year they sit on the same stretches of fence line and ignore others.

First back, that is now, are the Flame Robins (Petroica phoenicea), pictured left. The scientific name comes from the Greek petros meaning rock, oikos meaning dwelling place and phoenicius meaning scarlet i.e. scarlet rock-dweller – a nod to the habitat where the type specimen for robins comes from, Norfolk Island.

Robins usually roam the landscape as part of a mixed flock of birds. Later on in the season they will be joined by Scarlet Robins (Petroica boodang) forming a colourful and noisy group. At first glance the two species look identical but the Scarlet Robin is black (as opposed to grey), has a black throat and a large white flash on the forehead (pictured right).

At the moment the Flame Robins are mixing with Yellow-rumped Thornbills (Acanthiza chrysorrhoa) and European Goldfinches (Carduelis carduelis), pictured below. The latter, introduced residents to Australia, are found widely throughout Europe and Asia. I have not seen Goldfinches in these areas before.

The bush is getting cosmopolitan (or over-run).

I got lucky

May 11, 2020

Autumn is the time of year when for butterflies the result of all that frantic summer mating becomes obvious. There is now an army of caterpillars marching across the landscape devouring vegetation. It is a relatively easy thing to identify a butterfly. Their colours and shapes are very obvious, the number of species in any district is limited and there are a number of excellent resources for identifying them. The chance of identifying a caterpillar however is more fraught.

Yesterday I noticed an unknown caterpillar walking along a branch (pictured above). The difficulty in identifying it was that not only could it be the larva of a butterfly, it could also be the larva of a moth or not be a lepidopteran larva at all. So where do you start. For me, given it was a rainy Saturday morning I decided to go to one my favourite websites for butterflies and moths (http://lepidoptera.butterflyhouse.com.au) and simply scroll through the caterpillar pictures (not a very scientific approach I know).

After several hours of fascinating photos I was about to give up and there it was – a Meadow Argus caterpillar (Junonia villida), a local species. The Meadow Argus is a butterfy of Australia and the South Pacific islands. Generally orange/brown in colour the wings have blue ‘eye spots’ used to frighten predators away. On the underside of the forewings there are also eye-spots used for the same purpose when the wings are in a vertical position.

As far as caterpillar id goes, I got lucky!

Keeping the wolves from your door

May 9, 2020
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The current global situation has meant that I have much more time to cruise around photographing critters, and even more time to lie in wait for them. During a recent burst of gardening I found a hole in the ground and decided to wait and see what if anything appeared out of it (any excuse to laze away the day). Once the sun hit the entrance it wasn’t long before the resident appeared, a Wolf Spider. It took a further week of watching before I could get a shot of the whole spider outside of its burrow (see below) – stay-at-home protocols obviously also apply to spiders.

Wolf Spiders are one of the larger spiders in the district. They can be identified by their characteristic eye configuration (see previous blog) consisting of a bottom row of four small eyes with a top row of two large eyes facing forward and two smaller eyes facing backward. As previously mentioned they are ambush hunters rapidly chasing down prey along the ground from the burrows and cracks in the ground in which they live. And they are common. A walk at night in the bush with a torch will reveal a myriad of points of light reflected from the back of their eyes. Even divided by eight, it represents a lot of spiders.

A refugee from our recent burn-off

For those arachnophobes among us it may be hard to prevent these spiders getting close. The female spider carries the egg sac, and later the spiderlings, around on her abdomen. When the spiderlings are ready they send up strands of silk and disperse on the wind, often traveling large distances. A frightening thought? Think of them as an army of pest exterminators.