Nursery web spiders and their nurseries

The population of nursery spiders at the wildlife garden is particularly obvious now, as their nursery tents hang from their high positions from grasses and meadow cranesbill leaves, closely guarded by females. There are at least 20 nurseries scattered over the meadow at different stages of development. In some the spiderlings have already dispersed, after spending a few days safe inside their tents. This is what W.S. Bristowe had to say about the female after mating takes place:

During the first half of June the female may be see trundling along with a huge light-coloured egg sac under her sternum which is attached to her spinnerets by threads and is held in her chelicerae. At about the time the eggs are beginning to hatch, she loosens the outer covering and attaches it to a blade of grass. The she weaves a tent over it on the outside of which she stands on guard [...] The young emerge in late June or early July, after moulting once inside the egg sac. Now they cluster together in a ball inside the tent for a few days before moulting for a second time and dispersing.

I found the first nursery with already emerged spiderlings on the 20th of June. Bristowe was of the opinion that Pisaura will have two batches of eggs. Although the female below was carrying an egg sac on the 4th of July, I am not sure if this represents variation on the date of reproduction of different individuals as they mature, or evidence of a second batch.

Female carrying her disproportionate egg sac. They appear to walk on tiptoes holding it. I don't think the female is able to hunt while carrying her egg sac.

This spider has a fresh nursery web and appears to be manipulating the egg sac to allow the spiderlings to emerge.

Unlike the neat, smooth new tents holding clustered spiderlings the tent above has a few holes (made by the female?) allowing spiderlings to disperse. The spiderlings are clustered forming a ball just visible at the top right hand corner of the nursery tent.

The spiderlings are often clustered together in a ball like garden spider ones. The ones above look like they are ready to leave their tent.

If you click to enlarge the photo you might be able to see some tiny spiderlings on top of the tent already leaving.

I haven't found any information as to the function of the nursery web. Certainly it keeps the spiderlings dry during rain, and the mother is often found underneath also during poor weather. It could offer protection from parasites or predators. Many predatory insects will readily take spiderlings, including wasps, and it appears that the nursery web is not totally wasp-proof, as these photos on Flickr show.

Watching Pirate wolf spiders

I went to the wildlife garden with the intention of watching some wolf pirate spiders. These are spiders that often walk on water and are found in close association to wet habitats. They are wolf spiders and, although they make a silk retreat, they do not make a web for hunting, instead relying on an ambush strategy to capture prey. The species in the pond most resembles Pirata piraticus, the most common species. These spiders are found as adults from May to September.
 I sat by the edge of the pond, and was entertained by several pond skaters squabbling for a dead mirid bug.

But it wasn't long when I spotted a male pirate wolf. I took a photo, but he rapidly disappeared in the thick vegetation of the pond. These spiders have a very characteristic coluration, with a whhite edge around their thorax and abdomen and a background rich brown and greenish, with unpatterned legs. Males have paired white spots on the abdomen, while females also have a white V shaped mark around the middle of her abdomen.

Another smaller individual, also a male, crossed the pond rapidly. In a cursory view they do look remarkably like pond skaters, specially due to the pale fringe of the abdomen and the way they move on the water...

...but he crossed the pond again and I lost it too.

Then I spotted another one. This one looked quite shy and reluctant to move, and it sat hidden by the stems on the water edge.

 I got closer and gently enticed it to come out (top shot and below) and then it become obvious that she was carrying a large, white egg sac.

It then become obvious why the white stripes, these are very similar to the reflections of the water on the edge of the pond, and probably help concealing the spider to their predators, and possibly their victims.

A Stretch spider by the pond

I spent some time in the wildlife garden this morning looking and photographing pirate wolf spiders (post to follow) and watching pond skaters in the pond. I had noticed a pair of legs coming from under a yellow flag leaf, hugging it and I decided to inspect. As I turned the leaf I spied a large, wonderful female stretch spider of the genus Tetragnatha. The spider had its front and rear legs stretched to the front and rear, and held onto the leaf with her middle legs. She walked up and down the leaf, rearranging her silk threads, which I had possibly dislodged. She was quite a large sized and very colourful spider, with yellow and red stripes on her elongated abdomen, it looked so exotic and tropical!
  Out of the six British species of Tetragnatha, two are larger and more common and one of them associates with water, T. extensa, although detailed genital examination is needed for a secure identification.
 Tetragnatha have very large jaws, and the males using their modified jaws to lock the female's in place - and keep out of danger - when mating.
 You can see the folded fangs in this shot

And this is a scanned figure from Bristowe's The World of Spiders (1958), drawn by Arthur Smith, demonstrating the locking mechanism (male at the bottom)

I took this shot to give you an idea of the size of the spider

For a wonderful account of the mating behaviour and natural history of these spiders, go to the Spiderbytes blog.

Wildlife garden bug safari

After my encounter this morning with the basking Nursery web spiders, I popped back to the wildlife garden after a storm had passed and there was some promise of a sunny spell. The spiders weren't out, but I found a few interesting invertebrates about, including two new species for the garden.

A Peacock, which together with a couple of large whites were the only butterflies about.

 The first nice surprise were a couple of Green Thistle Tortoise Beetles (Cassida rubiginosa), which I had never seen before, both of them on knapweed:

Then I found some Rophalus subrufus, including a couple mating.

A Green shieldbug came out on the leaves to bask.

And then I came across some nursery web spiders, one of them a male prowling...

...demonstrating how agile they are moving across leaves, hiding behind them quickly if I moved a bit too fast or too close.

...and a placid female sunning herself on the oregano of the herb garden.

 Just before leaving, another new species for me, a very pale grass spider, Tibellus oblongus, contrasting with the green leaves.

Colourful nursery web spiders

The population of Nursery Web Spiders is thriving in the meadow of my local wildlife garden. I counted no less than 11 today, sunbathing in the long sunny spells between showers. They are striking, easy to spot spiders, that like to stretch to sunbathe like wolf spiders, but keeping their front pair of legs stretched forward together. Many were visible close to each other in various leaves of the lush vegetation, which made apparent how variable in colour they are, from ashy grey to brown and orangey or reddish. They all have longitudinal stripes, with the darker stripes on the cephalothorax. They will probably be mature or mature soon, so males would be capturing flies, wrapping them in silk and offering them to females, while they play dead in order to survive the encounter and make copulation more likely.

Male

Female

More information
British Arachnological Society page.

Do adult female house spiders roam?

As you gather from my last post, it is quite common to come across adult male house spiders, Tegenaria, roaming in search for females in late summer and autumn. Females are supposed to wait for them at the bottom of their web funnels. I was puzzled to find this fully grown, beautiful female inspecting my cat scratching post, in the open, an hour ago. Do females roam too?

Spider portraiture

It is quite flattering that several people have congratulated me over the years on the invertebrate photos I feature in BugBlog, thank you guys! I don't claim to be a photographer, but I am happy to share a few tips on the white bowl technique, which I regularly use on critters found around the house and garden, especially on non-flying ones. As today I found the first male house spider, Tegenaria sp., of the season, I thought a post on this topic was timely.
Before my daughter finished saying 'spider!' I got the little beast running across the kitchen floor into a little plastic pot. For this, I save any little plastic pot I come across. You know the onion salad pot from an indian takeaway? ideal! To hold the bug for a few minutes the pot does not even need to have holes on the top. I also have a 'proper' bug viewing pot (like the one featured in the photos below). My bug pots are always available on the side of the kitchen and I always carry one in my bag.
The second piece of equipment is the bowl. A flat-bottomed white bowl, like those used for soup, is ideal, as its sides help reflect the light. Better if there is a smooth transition from the bottom to the sides, as it will reduce undesirable reflections.
 I take the bug pot and bowl to the conservatory (or outside, weather permitting), as I like as much natural light as possible.

And push the cat out of the chair (sorry!).

 Then I remove the lid of the bug pot, put the bowl on top, turn it round to transfer the spider to the bowl surface.

I'd like to say that, although it is a common technique, I don't like to use the fridge to cool down the animal, I am impatient and I want to get the photos and release the animal as soon as possible. Many of the bugs are naturally slow and settle quickly on the pot, or stop long enough for the shots. Male spiders at this time of the year are challenging, as they are very jittery and require a bit of attention until they are posing well. Usually, tapping on the table will startle them and they will stop running around. Unfortunately, they often stop leaning on the side of the pot, so when you remove it, they are settled in awkwardly like so...

...which is not ideal. I move the pot slowly until the spider is in the middle and blow softly under the pot, until the spider spread its legs.

Now lets go to camera settings. I don't own a DSLR, just a bridge camera (Canon Powershot G12, if you are wondering), but you can achieve a similar effect with any portable camera. I first set the flash on, and increase the flash setting to +2, this is important if the bug is dark, as the auto flash setting will result on an overall dark animal and not a very white background. You might need to experiment with your camera to find the best flash setting.

No flash

Flash on to +1

Then I set the focal point to the top left hand side of the visual field (nearer to the flash itself), instead of the central position. This ensures the animal is not in the shade of the objective. If I didn't do this, once I cropped the photo, the bottom right corner would be grey, not white, as it would be shaded by the objective. You can simulate this on a cameral without this setting by focusing in the middle point and then moving the camera trying not to lose the focus so that the animal is located in the top left hand side of the visual field.
 Today, I experimented by holding the camera vertical, so that the flash light came exactly in front of the spider.
Set the camera to macro, and fire away. I usually take lots of photos, as I want to get the focus right on the animal's eyes and I try also several angles, which are often useful for ID purposes.
  I download the photos in the computer and do some basic processing. Crop the white/grey space out, adjust the levels so that the white background is actually white, remove specks of dust or dirt and sharpen a little. That's it!

Cropping

White level adjustment

 This one is my favourite of the session today. Although the white background is not perfect, as it is greyer on the right hand side, I like the spooky effect of the spider leg shadows.

Newborn Pholcus spider

A female Pholcus phalangiodes carrying eggs has been in the outside toilet for over two weeks. Today, I noticed her shuffling a bit, and when I looked, the first spiderling had been born and was sitting on the eggs. The spiderlings' folded legs and rows of eyes are clearly visible through the egg shells. When I returned five hours later, the female was holding a fuzzy ball of baby spiderlings.

For more on Pholcus on BugBlog click here.

Wolf spiders with egg sacs

Suring a sunny spell, the first wolf spider of the year carrying an egg sac - likely to be Pardosa amentata - run across the warm concrete in the garden. The silk on the egg sac was still bluish, indicating that it was very fresh. A little later I found another one sunbathing on the conservatory frame (below). A male kept approaching in full courting display mode, but she quickly lunged at him and retreated like saying 'go away, you are wasting your time'.
 Female wolf spiders as many other spiders display maternal behaviour. First, they carry their eggs wrapped in a silky egg sac until their spiderlings emerge. As these spiders move about in search of prey, this offers more protection to their eggs from casual predators than if the egg sac was attached somewhere and left on its own. Then, they open the sac when spiderligst are ready to hatch and allows them to climb on her back. The spiderlings will ride their mum for a few days before dispersing. These are sun-loving spiders, actively moving to and from sunny spots to adjust their temperature to higher than the ambient temperature in a similar way to lizards. Being carried about by their mother - both eggs and young - is likely to serve thermoregulation purposes, optimising the speed of egg and young development, as females of some Pardosa species have been shown to prefer higher temperatures than males and immatures.

Basking female.

Despite the mother's best efforts, wolf spider's egg sacs are often parasitized by tiny often flightless ant-looking wasps of the genus Gelis. Read this post by Chris Buddle to find out first hand about wolf spider egg parasites.

A Gelis wasp runs on the blue bin lid.

Click here for more wolf spider posts in BugBlog.

Fangs!

A rainy day, I look around the house for things to look up with the little digital microscope and I find the shrivelled shell of a spider, probably a Tegenaria, in the conservatory, behind a pot. I notice the fangs and look under the microscope. It is not the best photo, but I am quite pleased with the fact that the tiny openings at the end of the fangs (where the venom comes out) are just visible. Click here for a scanning electron photograph of these openings. The fangs act as hypodermic needles, injecting the venom inside the prey's body. The teeth that help hold the prey while the venom is injected are visible at the bottom.

Adult pair of Pholcus phalangioides

 In the last few days, I have been keeping an eye on a pair of Pholcus phalangioides in my outside toilet. They are a male and a female, and given that both appear to be adults I guess the male is waiting for the female to become receptive. I got a close up of the male, showing its almost circular caparace and its palps (above).

Pholcus phalangioides. Male on the right, not its elongated abdomen.