Christmas spider - Austracantha minax

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Christmas spider - Austracantha minax

This orb-weaving spider from the Araneidae Family was previously known as Gasteracantha minax, but has now been placed back into its original genus (first described in 1859), where it is the only species. Christmas spiders, so named for the time of year they normally make an appearance, range across the southern and eastern regions of Australia, where they are also known as Jewel Spiders, Six Spined Spiders or Spiny Spiders.

These spiders can occur in huge numbers and string their vertical webs between low shrubs making it impossible to walk through parts of the bush without becoming covered in their webs. Fortunately the spiders quickly drop to the ground as you make contact and if you walk slowly, they will see you coming and scamper upside down along their support lines to avoid a collision. However, they are only small (females to 8 mm, or little over 1/4” head/body length, males are half that size) with tiny legs making their progress correspondingly slow.

Their markings are multi-coloured and certainly jewel like, however this stage is mainly from December to February, when later arrivals lack any markings and are a very dark brown to black. This change takes noticeable pace from the beginning of March until they disappear around the end of April. A possible reason this color change is the better heat absorption of dark colours during the cooler autumn season, but this is purely speculation and currently just an observation.

Garden Spider - Eriophora biapicata

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Garden Spider - Eriophora biapicata

This spider is the sharp horn of the naturalist dilemma, which I shall attempt to explain. Eriophora spiders are large master orb-weavers, building the common wheel-like webs that everyone has walked into at some stage of their life and found themselves face to face with a very bulbous arachnid, which despite your level of panic, is as intent of exiting the situation as you are yourself. Fortunately these spiders are very docile and when examined closely are not that scary, although the male which is also large has a more sinister appearance, but are not so commonly encountered. Eriophora belongs to the large Araneidae orb-weaving family, however in Australia Eriophora is a small genus with five species and only one of these resides in Western Australia, namely E. biapicata. So where could you possibly go wrong?

Above are a number of photos that indicate the huge variation that exists within these spiders. I have numerous photos of E. biapicata, but as I was adding to my collection I quickly became confused as to identity, which continued to grow as did my reference collection. How could a single species be so different, not only in coloration, but in structure and habit. So I sent a number to someone who should know, ie Ron Atkinson of the University of Southern Queensland, who assured me that this level of variation within a species, also applied to other spiders within this genus. So there you are, they are apparently the same spider and therefore the subject of this post!

Eriophora spiders are commonly called Garden Spiders and the female can have a swollen abdomen of between 2-3 cm (1") diameter and are renowned for building these large webs only to take them down before dawn. This certainly applies to many of the local garden spiders and their temporary webs indicate that they are in fact Garden Spiders and not from another genus. However, in the Esperance region this does not always apply as some will maintain the web 24/7 and will often remain on the web during the day. So either their predators are not common in their area, or they have fewer animals crashing into them. The black and white spiders above tend to do this more so than the other colors, and are commonly encountered around the base of granite outcrops, saltlakes and mallee regions, but less so in heathland where other color forms (who usually do remove their webs each day) are more common.

These spiders either die or hide in a warm place during cold winter weather, so at this time of year, you can usually walk around your garden without the fear of literally walking into one. To see how they form the main web structure, note the strong line at the top of the web stretching from one sturdy support to another, from which the wheel part is hung. In order to form this strong line, the spider hangs from one support by a short thread, then releases another into the evening breeze that hopefully carries it across the intervening gap until it sticks on something the other side. The spider then walks across and attaches this thread end to another strong support. Above is a photo of the female casting a thread into a breeze.

Male spiders are labelled male, whilst the more obvious females having the large rounded abdomens are not. For interstate readers, Eriophora biapicata is also found in the NT, SA, VIC, NSW and Qld., but to complicate matters so are other similar looking species.

Banded Orb-weaving Spider - Argiope trifasciata

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Banded Orb-weaving Spider - Argiope trifasciata

In Australia the Banded Orb-weaving Spider is recorded only from Queensland and Western Australia, which suggests it is more widespread, but is either rare or poorly collected. In the Esperance region they are to be found on round leaf sedges in low-lying areas that may flood during winter; here they build a small orb web usually within 60 cm (2') of the ground. Like many orb-weaving spiders, there is usually an influx of species during vegetation regrowth after a bushfire, and it is during these periods these spiders are commonly encountered.

Most of the above photographs were taken of a solitary female that had built a web on sedge around a small dam. Apart from a couple of male Banded Spiders, they were the only representatives of this species there, but this year (although the original female has probably died), there would be a dozen or so immature females, all with similar banding and coloration, but currently only around 1 cm (3/8") body length. The larger female was closer to 2 cm (3/4") in length. The males of last year were little more than 5 mm (1/4") in body length and lived on the outer edge of the female's web.

The female mostly remains in the center of the web, with the legs arranged in the shape of a cross and very similar to a close relative, the St. Andrew's Cross Spider (common elsewhere, but not yet seen by me in this district). If threatened, she will drop from the web to the ground and quickly disappear. When an insect flies into her web, she is amazingly fast to grab and wrap it in silk, she then cuts it free, takes it to the center of the web where she bites it.

Sometimes this spider will make a partial stabilimentum (a line of dense white silk built onto the web, which is thought to warn flying birds to avoid collisions). However in this district, adult spiders commonly do not bother and immature spiders rarely ever construct one.

Although brightly colored spiders, they largely go unnoticed unless searched for, as their banding blends into the multitude of light and dark shadows generated by the fine leaf sedge. However if you are in that type of habitat, look around at knee height and you may find one. They are regarded as harmless to humans and are not aggressive.

Araneidae - Argiope protensa

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Araneidae - Argiope protensa

A spider widely distributed across southern Australia and closely related to the St. Andrew's Cross Spider, Argiope keyserlingi. This species has an elongated body that is officially recorded as being to 1.5 cm (little over 1/2") in length (excluding legs), but in this region the spiders I encountered were commonly 2 cm (3/4") in length, with a particularly large specimen closer to 3 cm (1"). They all occur on the same granite outcrop, but in different habitats with probable different prey, which may help explain the difference in nutrition and growth rates.

Another variation is the stabilimentum (dense band of silk built by the spider into the web), all webs other than one, had none at all and interestingly the one that did, was made by the smallest spider (1.5 cm in body length), but resided at the base of a Hakea clavata shrub Proteaceae - Hakea clavata on bare rock. This barren habitat would likely have fewer visiting prey species, which in turn would possibly affect the spider's growth development. An interesting study of the stabilimentum (Behavioral Ecology), suggest it is intended to warn day-time flying birds of the web's presence and so avoid it. This would seem reasonable in the circumstance, as birds both insectivorous and honeyeaters do periodically visit these isolated plants, so would need to be made aware of the web and so avoid it.

The photos above labelled male, female and the egg-sac, belong to a spider family residing on an isolated clump of sedge. The male who was about a third the size of the female, had his own web, although much smaller than the one occupied by the female (both were within 50 cm or around 1'6"of the ground). The male caught a flying insect while I was watching; he bit it first, then removed it from the web and carried it back to the web center, where he then wrapped it (most spiders usually wrap the spider where caught and bite them later). The egg-sac was a few centimetres off the ground and had the unusual feature of a lid to permit the spiderlings escape.

A very interesting spider that was new to me and I thank Ron Atkinson from the University of Southern Queensland for his identification assistance.

Tent Spider - Cyrtophora cylindroides

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Tent Spider - Cyrtophora cylindroides

A spider better known for its web than the spider itself and despite the webs complexity, it is acually made by an orb-weaver. Commonly built within a metre (3') from the ground, the main orb (as it invariably comprises a network of them) is drawn up to a peak to form a tent-like structure. The peak is decorated with debris, often including a dried leaf, making a reasonably weatherproof retreat for the spider. As additional support for this structure, there are a multitude of supporting threads forming a very tangled surrounding framework, making access from predators and photographers alike extremely difficult.

The female's body length (excluding legs) is around 1.5 cm (1/2") and the male is less than half that size. There is a communal northern Cyrtophora species that forms very large webs to include many individual spiders of both sexes, but Cyrtophora cylindroides only has a single female, although more than one male can usually be found somewhere within or on the edge of this tangled orb-web complex. However the male having a small body with fine legs can be difficult to spot.

Currently there are less than ten Cyrtophora species recorded for Australia, with WA having only two comprising this species and the northern communal one Cyrtophora moluccensis. However Araneidae, the family of which Cyrtophora is a member, has over 30 genera and approaching 300 species.

Garbage line spider - Cyclosa species

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Garbage line spider - Cyclosa sp.

An unusual small spider, no more than 1 cm (3/8") overall length, with a relatively long fat abdomen (as long as the rest of the spider including its legs), plus with two side appendages. It makes a small circular orb web where it constructs from several threads, a horizontal line across it from which it hangs insect debris (hence the common name). The spider whose outline is broken by its unusual shape, sits between the garbage and appears to be just another piece of it and is thereby disguised from predators.

Whilst taking close-up photos of the spider, a pesky little bushfly fell into the web, where upon the spider made a leisurely stroll to it, quickly disentangled it from the web, then matter of factly carried it back to the web center, where it was promptly wrapped in silk and bitten, or possibly re-bitten (if so then for much longer).

The habitat was near the summit of 1 metre (around 3') high sedge surrounding a small dam. I only encountered the single female, so presume they are not particularly common, although the area was burnt in a bushfire during the summer of 2005, so maybe early days for recolonisation. I encountered a small woolly egg-sac close by that matches the description given for those made by the garbage line spiders, so hopefully there may soon be more.