Meanwhile in Cape Town … the spider invasion

Friend Jane says there’s been an influx of Nephila fenestrata, the black-legged golden orbweaver, into suburban Cape Town. Where she lives, the strong webs of these spiders are being strung across walking paths as well as gardens. Luckily, it’s easy to gently reposition them manually, and the spiders aren’t disturbed.

Nephila fenestrata

Nephila fenestrata female, ventral view; photo by Jon Richfield, Wikimedia Commons

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Female, dorsal view; photo by Jon Richfield, Wikimedia Commons

She says:

It’s only recently that they’ve decided to go suburban but they seem to be in many gardens now, although not in quite such rampant numbers as mine – people are beginning to come and take pictures.

These spiders are native to southern and eastern Africa. You can see a photo of the large and strong web at Biodiversity Explorer, which says:

Nephila fenestrata, the black-legged nephila, occurs over most of South Africa, excluding the arid central and western regions, and is the only species of Nephila to occur in the Western Cape. Since 2002 this species has crossed over the Hottentots Holland mountain range and is now the most commonly seen orb-web spider on the Cape Peninsula. It can be seen from January till the end of June or even to the end of August, usually in forested areas or near areas with trees allowing for suspension of their large orb-webs. In Kirstenbosch and Newlands Forest one can easily see 30 or more of these spiders on a walk.

Wikipedia says of Nephila in general:

The webs of most Nephila spiders are complex, with a fine-meshed orb suspended in a maze of non-sticky barrier webs. As with many weavers of sticky spirals, the orb is renewed regularly if not daily, apparently because the stickiness of the orb declines with age. When weather is good (and no rain has damaged the orb web), subadult and adult Nephila often rebuild only a portion of the web. The spider will remove and consume the portion to be replaced, build new radial elements, then spin the new spirals. This partial orb renewal is distinct from other orb-weaving spiders that usually replace the entire orb web. In 2011 it was discovered that the web of Nephila antipodiana contains ant-repellent chemicals to protect the web.

Typically, the golden orb-weaver first weaves a non-sticky spiral with space for two to twenty more spirals in between (the density of sticky spiral strands decreases with increasing spider size). When she has completed the coarse weaving, she returns and fills in the gaps. Whereas most orb-weaving spiders remove the non-sticky spiral when spinning the sticky spiral, Nephila leave it. …

The circular-orb portion of a mature [US] N. clavipes web can be more than 1 metre across, with support strands extending perhaps many more feet away. In relation to the ground, the webs of adults may be woven anywhere from eye-level upwards high into the tree canopy. The orb web is usually truncated by a top horizontal support strand, giving it an incomplete look.

Adjacent to one face of the main orb there may be a rather extensive and haphazard-looking network of guard-strands suspended a few inches distant across a free-space. This network is often decorated with a lumpy string or two of plant detritus and insect carcasses clumped with silk. This ‘barrier web’ may function as a kind of early-warning system for incoming prey or against spider-hunting predators, or as a shield against windblown leaves; it may also be remnants of the owner’s previous web. At least one reference explains the suspended debris-chain as a cue for birds to avoid blundering into and destroying the web.

Indeed, some webs have captured small birds, but no one’s found that the spiders actually eat the birds.

I’m particularly fond of the species name for this spider as it is a Latin version of my surname 🙂

Jane says it’s on for young and old in a small patch in her garden:

I would never have thought 4 square metres could have held such variety. I was out in front chatting to my neighbour about how one of the nephila orbs had caught a gecko lizard and sucked out all its juices, leaving the dehydrated corpse in the web, which she’s still fiercely guarding. ‘Look,’ says Louise, and lo and behold behind that orbweaver a praying mantis is stalking a white butterfly – such drama – but the butterfly did escape.  Some butterflies have flown smack into the orbweaver’s curtain, but a surprising number manage to avoid it. A gorgeous black bumble bee managed to duck and dive, as do most of the damsel flies. Mind you, a little white eye bird (a tiny passerine) nearly copped it, but seemed to have rebounded off the web and got stuck in one of my sheets, which was hanging out to dry. I come indoors from the dazzling display to make a cup of tea and a triumphant jumping spider staggers across the kitchen counter with its trophy, a fly bigger than itself. Go spider! I’m having to move strands of orb nearly every morning or I’d be trapped in the house – great colonisers, these ladies.

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Dwarf sea hare at Woody Head

Thanks to Peter Scharf for the photo of this dwarf sea hare, Aplysia parvula, taken while he was snorkelling off the reef at Woody Head in early January 2017.

Sea hare, Aplysia parvula; photo by Peter Scharf

Dwarf  sea hare, Aplysia parvula; photo by Peter Scharf

The Sea Slug Forum gives information about this species, plus a photo of a juvenile with the shell visible. The mantle grows over the shell as the animal matures. These sea hares, vegetarians all, are small, up to 6 cm (just over 2 inches) in length.

Another goody at Woody!

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No Tassie devil trip this year

I’m disappointed that the Tasmanian Devil Scientific Expedition in March is not going ahead this year. The chief scientist, Associate Professor Menna Jones, has won a Fulbright scholarship to pursue studies in the US. Good on her – she is smart and capable.

The devil facial tumour disease’s progress is slowing down and it still has not reached the west coast of Tassie – good news. Research is still needed, so the trip has been postponed until 2018. If you are interested in helping out, click on the link above to find out more from Curious Traveller’s website.

 

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Another Woody Head nudibranch

I’d already seen Sebadoris fragilis at Flat Rock, Ballina, but it’s always a joy to see any nudi, anywhere, anytime.

This one was found by Peter and Linda, snorkelling off the rocks at Woody Head. Thanks to Peter for the photos.

Sebadoris fragilis, Woody Head; photo by Peter Scharf

Sebadoris fragilis, Woody Head; photo by Peter Scharf

Sebadoris fragilis, Woody Head; photo by Peter Scharf

 

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Snail parasite blowfly

We may not like every type of animal we see, but they all have their place in the scheme of things. I’m personally fond of things others may not be – just call me contrary.

Armenia  (the snail parasite blowfly) is certainly colourful and presumably to be thanked by gardeners for helping keep snails under control. There are several species, and this one is likely to be A. imperialis, the yellow-headed snail parasite blowfly.

amenia_4

amenia_1  The Queensland Museum says:

Many blowflies attack invertebrates, such as insects and snails. The Snail Parasite Blowfly often rests on rocks and fallen wood. Females give birth to large, well-developed larvae that are thought to be parasites of land snails. Common in open and closed forest in eastern Queensland and New South Wales.

Length 10-15 mm. The bright yellow head contrast with the thorax and abdomen which are metallic green or bronze with silvery-white spots. The wings are clear with dark bases.

Thanks to Greg Spencer for the heads-up and the photos, taken down the road in Rock Valley.

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Finally – a Richmond birdwing!

I’ve been waiting to see the beautiful Richmond birdwing butterfly (Ornithoptera richmondia) since I moved to the Northern Rivers (18 years ago). Admittedly I have not tried very hard – didn’t go to likely places of encounter. But now I have seen one – outside the lounge room window! It’s a great, colourful thing with a most graceful, swooping flight on big wings. I thought I’d never see one, as it is a threatened species. This is a male, in the flowering frangipani tree.

richmond-birdwing-2

Richmond birdwing butterfly (male)

The maximum wingspan is said to be about 10.5 cm, and this one seemed about that. The female is not quite so colourful, but has a bigger wingspan (up to 11.5 cm). The green  of the top of the wings of the male (photo below) first caught my attention as it sailed by.

richmond_birdwing_butterfly; photo by Department of the Environment, Water, Heritage and the Arts

Top view of male Richmond birdwing butterfly; photo by Department of the Environment, Water, Heritage and the Arts, Wikimedia Commons

The species is threatened in New South Wales, vulnerable in Queensland, according to Braby’s Complete Field Guide to Butterflies of Australia (CSIRO, 2016) (contrary to Wikipedia).

The Richmond Birdwing Conservation Network has a mission to increase the numbers via increasing the host plant (the Richmond birdwing vines: Pararistolochia praevenosa in the lowlands and P. laheyana in the higher areas) and also the habitat that the vines and butterflies – at all stages of the life cycle – need). The FAQ of the network gives a lot of information about the butterfly, its lifestyle and range. A short version is :

  • The life cycle is a little different in higher and lower altitudes. At my place (lower altitude, below 600 metres), there are two breeding seasons when the adults emerge: between September and November and then from January to March (long daylight hours, high temperatures and high humidity).
  • The adult butterfly lives for 4 to 6 weeks, while the pupa (as long as 7 cm) lasts for about 28 days in the warmer weather, longer in colder weather.
  • The female lays 60-100 eggs on different leaves of the Richmond birdwing vine. From up to a few kilometres away, she detects certain chemical signals in the vines that indicate they are at a stage where the caterpillars can eat them.
  • The vine is disappearing due to land clearing – once it disappears, so will the butterfly. I assume that the vine is somewhere in the vicinity of the house so I’ll have to keep an eye out for it, and for some pupas and more adults. But ‘[r]esearch has shown that the male will travel up to 4 kilometres from where it pupates while the female will travel up to 30 kilometres from where it pupates’, so it may not be that close after all.
  • The adult’s yellow and red colours tell predators (pied currawong, noisy pitta, wasps) that the butterfly is toxic and should not be eaten.

When I first saw the butterfly fluttering by, I took a quick look on the ‘net and thought, ‘Holy moly, it’s a Cairns birdwing – but what is it doing here?’ Further investigation showed that it was our very own Richmond species. The Cairns birdwing (Ornithoptera euphorion) is the largest endemic butterfly in Australia, up to 18 cm in wingspan.

As chance would have it, I have a couple of pinned specimens of the Cairns species, inherited from a friend (thanks, Cate and Bill!). You can see why I made that mistake.

(Top) Female Cairns birdwing; (bottom) male Cairns birdwing

(Top) Female Cairns birdwing; (bottom) male Cairns birdwing, Ornithoptera euphorion

 

Exciting!

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Fearsome fangs

I was sorting out stuff in my laundry this morning. It’s open to the outside so I guess it’s no surprise that this fellow should be in a bucket.

Funnelweb

Funnelweb

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Venom drops are just visible on the end of each fang.

funnelweb-spider-in-bucket_andrewIt was quite assertive, rearing up backwards in classic striking position. The venom drops on each fang were clearly visible, though not so much in the photo above. The rearing posture and venom drops distinguish it from the mouse spider, which is another biggie in our area.

You do not want to mess with this spider – it’s a funnelweb, not the Sydney funnelweb but still dangerous with possibly fatal consequences if you get bitten. It’s been quite a dry spring so the spider was probably seeking moisture as well as shelter in the daytime.

Funnelwebs are nocturnal, so I probably gave this one a shock. You can read about them here, and about mouse spiders here. Interestingly, dogs, cats, adult mice and guinea pigs are immune to the venom. The theory is that primates (including us humans) were not around when these spiders initially evolved so the toxicity is an accident.

I poured it out into the bush at the back of the property. The Queensland Museum, whom I queried re ID, says they tend to come back to their familiar places, so I might find it again. The laundry is due for a big clean-out in any case, and I’ll be wearing boots and gloves to do it.

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