Tuesday, December 3, 2013

My smart little orb weaver

A new spider season. As summer starts, the webs are getting bigger, and there are lots of them. Last season there were few orb weavers around. After a wet winter this year, there are plenty. Three of the orb weavers I am checking every night are three different species. I have become extremely fond of the little spider in this blog, who I've watched grow from a speck to near her full size, a body length of about 10 mm.

Intelligentsia is a clever little spider. She built her web across the door into my Garret, the studio where I write. I have 'trained' orb weavers before - moved the main structural lines which were in the wrong place a few times, and the spider seems to get the idea. I did the same with Intelligentsia. For a month or so now, she has built her web with a curved 'doorway' for me just high enough to go in and out with ease. Unfortunately, husband Damian forgot to duck last week and ruined Intelligentsia's web. Fortunately, as he bumbled into her real estate during the day, she was safely tucked away in her retreat.
[Click on the images for full size.]


Intelligentsia has the bumps on her abdomen, front and rear, typical of her species, Eriophora pustulosa. Her underside has the black patch which also distinguishes the species. This is the view I get as I leave the Garret. 


Intelligentsia comes out each night, repairs her web (or rebuilds it if some silly man has forgotten to duck). She lives the usual active life of a spider, including catching, killing and and devouring insects.


During the day, Intelligentsia retreats to a patch of old web from a long-gone cobweb spider in a gap in the verandah roof. One leg is always in touch with her orb web, just in case dinner arrives early.


I'll introduce the other two orb weavers in the next blog. And keep you informed on Intelligentsia's life.

Monday, May 27, 2013

The final weeks of Wonderful, the garden orb weaver.

Wonderful was a garden orb weaver, Eriophora pustulosa. I told of her life in a previous post, The story until here ... She hung around on her web all summer, getting larger and fuller in the abdomen until she was very fat (for her size). Every night I photographed her. (All images enlarge if you click on them.)



Then one night she was gone. I checked throughout the night and in the morning and throughout the day. There was her retreat, silk lined and spiderless.


The next night she returned. But the huge abdomen was now very thin. Somewhere nearby there was an egg sac. I started hunting. These spiders are known to be very good at hiding the egg sac, but then again, I'm a master spider watcher. I knew I'd find it.


Each night she spun a web as usual, and usually took it down before morning. Each day I hunted for that egg sac.


She fed night and day and started to regain condition. I kept hunting.



It was a horribly dry summer, so on hot days I watered her. As soon as the light sprinkles from the hose stopped, she emerged to drink. I hunted some more.


She hung around, looking beautiful. The leaves started to fall from the bushes, but no egg sac was revealed. This photo ...


... was the last I took of her. The next morning she was gone. I couldn't find any trace of a body. And the egg sac? I'm still hunting.




Saturday, March 9, 2013

Geelong's leaf-curlers - simply stunning


We went to the Geelong Botanic Gardens on Monday was to see the pelargoniums. It was a stunningly wonderful surprise to see the giant ferns and palms decorated magnificently by the webs and retreats of lots of Australian leaf curling spiders (Phonognatha graeffei, family Araneidae). All photos were taken by Damian Kelly.


These incredible spiders weave a part orb web and then draw up a leaf to create their retreat. They choose a fresh leaf from the ground below their web site, and then haul it up. Spiders have been witnessed lugging leaves up to four times their own weight. 

When in place, they stitch and tension the leaf, the tension in the silk curling the leaf into a cylindrical retreat as it dries out. Drier leaves are harder to curl breaking easily as the spider tries to bend them.


 Research with leaf curling spiders has shown they select their leaves very carefully. Under test conditions, some decided, later in the weaving process, to remove a dry leaf to replace it with a moister, greener leaf. When a tad on the lazy side, or fortunate enough to have the opportunity, a leaf curling spider may choose to haul an empty snail shell into the web instead.

Look how beautifully she holds onto her web with her front legs.


 I suspect the smaller spider is a male approaching the female's leafy retreat.


The males cohabit in the leaf retreat with immature females, waiting for her to moult. During that vulnerable window, he mates safely. Males will also cohabit with mature females and respond agonistically to rival males. But it’s not all rosy for the male Phonognatha. Females may eat him anyway.

Oh, and while we're talking about the wonderful Geelong Botanic Gardens, here are some of their pelargoniums. The only thing I enjoy photographing more is spiders.





Tuesday, February 26, 2013

My garden orb weaver lives up to her name - Wonderful

Wonderful, a garden orb weaver (Eriophora pustulosa), is living a very active life. (See the previous blog for her introduction.) Last night, she was hanging around on her web, just as garden orb weavers should. 

Please click on the images - I'm rather proud of these!


She collected a lots of food on a hot, moist night - the first rain for months had just started dribbling. She was soon feeding on two wasps she'd bound together.


Another wasp flew into her web - she rushed down the silk and rapidly enshrouded her new prey in silk. Having injected it, she left the struggling wasp to die while ... 


 ... she returned to dinner.


The rain started. She headed under a leaf at the edge of her web.


And took up her usual resting position, one foot on her main web thread to detect any newly ensnared insect.


When the rain got heavy, she bound the leaves around her into a shelter. And there she sat out the storm.


Love this spider! She's Wonderful!


Monday, February 25, 2013

She's Wonderful - I have an orb weaver!

This summer has been horribly dry and hot. The spider numbers are woefully low as are, not surprisingly, the insects. I thought I had no orb weavers.

I had seen hints of silk of one at the end of the verandah, but had never seen her. Tonight the silk was reflecting clear - it was fresh and crossing a span of two metres. She had to be there somewhere. Trying to follow the silk, I felt something against my arm - something about the size of a mature female garden orb weaver. I moved away immediately, hoping that I hadn't hurt her web. And I found her!

She's Wonderful! The two protrusions on her 'shoulders' and then more on the end of her abdomen tell me that she's an Eriophora pustulosa. She had dashed over to the edge of her silk line, attached to which was only the remains of what had been a full orb. She'd clearly caught prey earlier in the evening.

I couldn't get a good photo without disturbing Wonderful, so you'll have to make do with bum-shots. She's repairing her web - you can see the globules of glue in one silk. She wouldn't come out of the protection of the leaves while I was there.



I have been negligent about blogging - I've been preoccupied with completing my PhD thesis (not about spiders) and then redrafting it for publication as a book. But that is done and my spiders can take priority again. There are so many fewer this year than usual, but of course there are the daddy long-legs (Pholcus phalangioides).


And I always have my favourites, the blackhouse spiders (Badumna insignis). They've been breeding with gusto.


Their stories will be told here. I will also include photos from those who read this blog and send me images. The Spiderblogger returns!



Sunday, September 23, 2012

The Redback Wrangler and the Film Star

Usually, red-backs are very common around Castlemaine. They're pretty common all over the east coast of Australia. Usually. But not this year. My arachnid guru, Alan Henderson, needs some redbacks for a film commission and put out a call because no-one could find them. Not one, not anywhere.

A member of the tangle-web Theridiidae family, the redbacks (Latrodectus hasselti) are closely related to the American black widow (Latrodectus mactans). I had all but given up on finding redbacks for Alan when I was tidying some pot plants for an elderly neighbour, Nina. There was a most unusual web in one of the pots. It was a funnelled web, shiny, like that of the theridiids, but with a distinctive funnel, which is not their usual style at all.  I took my new spider home and named her Arachnina after my neighbour. That night I shone the torch on the owner, and there was no doubt that she was a redback.



Enter the Redback Wrangler. 


Alan's daughter, Caitlin, came from near Melbourne to collect Arachnina. This is a rare image of a Reback Wrangler at work.


Arachnina was collected into a container, with her web and retreat, ready to make her trip to Queensland to become a film star. Meanwhile, one of the many scouts I had out looking for redbacks had turned up with an understudy, rather unceremoniously enclosed in a jam jar. The Redback Wrangler made our new spider more comfortable with twigs and leaves. The understudy soon started spinning herself into a safe retreat.


Soon after Caitlin had left, I received a phone call from another scout. A third redback had been located. Having received detailed instructions from Alan in addition to having watched Caitlin, I venture forth tomorrow - I get to be The Redback Wrangler.

Watch this space - Alan has promised a really good photo of Arachnina. A good photographer can make a film star look stunning. I let you know about her starring role when it is public knowledge. 

I know you are all intrigued to know what the partner of a Redback Wrangler eats. Admit it, you have always wondered. Here is the evidence of the shocking truth. Adam had a sandwich of thick vegemite, tomato and lots of pepper on wholemeal. I kid you not!

Wednesday, September 5, 2012

The saga of the golden orb weaver egg sac

I am waiting eagerly to see if the golden orb weavers emerge again this season. It's a real mystery what is going on. The summer of 2011 brought an influx of golden orb weavers such as the town had never seen before. Last year, there were none. As spring is springing, the obvious question is: will they return? And why weren't they here last year? One theory is given below. This year will tell if it's right! And the other mystery - how did the daddy long-legs know about the feast on offer?

First, a recap. When we moved to Castlemaine in Central Victoria, Australia, in April 2011, there was a glorious adult female golden orb weaver (Nephila edulis, family Nephilidae) at the front door to greet us. So she was named Welcome.

(click to enlarge)

With a body length of over 2 cm, she was huge. Not long after, Welcome produced a golden egg sac in the bushes nearby. It was already well into winter.


The first frost came and the morning sight was welcome dropping from her web. She recovered in the day's warmth, but the next day's frost killed her.


I watched that egg sac, checking it every day. Nothing happened throughout the whole winter. Up in Kalimna Park, where I was watching another half dozen Nephila, three made egg sacs, and all disappeared with the frosts. 

Now, Welcome had spun her egg sac in the wire on a garden arch which was in the wrong place for my garden design. To move it would have wrenched the egg sac from the plants, so I carefully cut the wire and placed the egg sac on the little front porch. Didn't think that through, did I? When the young hatched, they would use the breeze to disperse - and there's only one way the breeze could come into the enclosed front porch - from the front, carrying them nicely straight into the living room. This is what happened:


The egg sac had faded when I cut it lose in September 2011 and placed it on the porch. It was not until early January, in the summer heat, that I noticed a living bundle near it. Young, hundreds of them. I tried counting from the image below, but gave up.


Over the next few days, they spread and regrouped continuously, little white bodies appearing in the mass of brown as a mess of tiny shed skins appeared below. They were moulting, the slightly larger freshly moulted young showing off their beautifully marked white abdomens - only visible when I enlarged the photographs.


At the end of the week, they were well spread, never to regroup again.


A day with a light breeze and they dispersed on their tiny filaments of silk. It was then I realised that I was an idiot. They could only be blown into the house as a breeze doesn't come from the house out into the world. And they did - hundreds of them into the living room. All over the furniture. All over the ceiling. While they were still in groups, I collected them on brooms and other soft objects, leaving them outside to disperse again. But they spread, meaning it was a matter of collecting them one at a time. They were all over ornaments, such as this little one on the cage of a music box with toy songbirds.


But I was not fast enough. The greatest mystyery of all: within a few hours, five daddy long-legs spiders (Pholcus phalangioides, family Pholcidae) had gathered in the front corner of the lounge room where most of the young landed. I have no idea where they came from. We have a lot of daddy long-legs, but there were none in the living room that I had noticed. The daddy long-legs were having a feast. How did they know to come?


Spiders never cease to amaze and entertain me.

So now I wait. None of these young grew to adults during that summer. Despite the huge numbers in autumn 2011, there were none last autumn (March / April in Australia). Will any of them appear this season? 

Note on the confusing daddy long-legs critters:

An American reader has asked about the daddy long-legs in the photo above. Is it a spider or a non-spider harvestman?

Two different groups of animals are called daddy long-legs, the spider version and the harvestman version. Both have eight long spindly legs. Both are arachnids. I gather Americans are more likely to call the spider version 'cellar spiders'. 

The differences: spiders have two body segments with the legs coming from the front bit, the cephalothorax. Harvestmen only have one body segment.  The spider version make webs while the harvestmen don't. Spiders are much more likely to be inside the house than harvestmen. I photographed huge harvestmen in Texas.



If you look at the image on the blog, you'll see the daddy long-legs has two body segments while the harvestman above has only one. Because of the confusion, arachnologists usually refer to the spiders as pholcids and don't use the 'daddy long-legs' common name.


References:

A great reference for Australian spiders is being developed at Arachne.org.au:

http://arachne.org.au/

This site is a working draft for "A field Guide to the Spiders of Australia" by Robert Whyte and Dr Greg Anderson for CSIRO Publishing due to be published in 2014-15.

I'll be using it as my prime site for classification from now on.

Postscript: Greg Anderson has sent me a fascinating paper on Nephila. It seems the questions I am asking about N. edulis are not answered - yet! Plenty of research to do which can be done by ordinary people out there watching them. 

"Given the large number of studies that have focused on the behaviour and evolutionary biology of Nephila spp., it is some- what surprising that little work has been undertaken on their population biology. In the Sydney region, adult female N. plumipes are univoltine, appearing in late December to February (depending on the year), and reproduce from late summer to autumn (February–May) (Austin and Anderson 1978; Elgar et al. 2003a). From June to September (winter–early spring) the population comprises a range of immature size classes, and a declining number of adult females that have all disappeared by August–September. This pattern becomes more complex in the northern, tropical part of the distribution of N. plumipes, where the breeding season is more prolonged, and populations may be bivoltine (A. Austin, personal observation).

Far less is known about the population biology of N. edulis, which occurs throughout the arid interior of the continent (Fig. 87). In arid regions this species appears to have more tran- sient populations, where dense aggregations of adult females will occur at a particular site in one autumn and then disappear, often for many years (A. Austin, personal observation)."

Reference: Harvey, Mark S., Austin, Andrew D., & Adams, Mark. The systematics and biology of the spider genus Nephila (Araneae: Nephilidae) in the Australasian region. 
Invertebrate Systematics, 2007, 21, 407–451