A worldwide community photographing and learning about wildlife
Project Noah Nature School
Argiope luzona
Argiope luzona (Walckenaer, 1841). When I spotted this female Signature Spider this morning, I noticed, as I approached that there was something slightly odd about its Stabilimentum (web decoration) and the oddities became clear as soon as I got a little closer. It is common knowledge among Argiope enthusiasts that the stabilimenta are woven from the same silk that is used to wrap prey and the linear components of Linear and Cruciate Stabilimenta are woven in a “zig-zag” style. I have been trying to take pictures of the different types of web decoration and have been including them in a series of spottings. In the most recent spotting of the series, on Jan 4th - https://www.projectnoah.org/spottings/14... I showed pictures of two types of “zig-zag”. The most common type is very clearly defined and sharp looking, but there is also a less common type which is still recognizable as zig-zag, but is very “fuzzy” or “wooly. I don’t know if there is specific nomenclature for these different zig-zag styles, but if there isn’t, there should be. So, returning to the stabilimentum in my photos from this morning, what are the oddities which make me want to include it in my series? Well, using the “X” shape of the stabilimentum, please look at the bottom right part of the “X”. You will see that the zig-zag starts in a neat and sharp looking style. Then the bottom left section of the “X”, by comparison, looks less sharp. The top right of the “X” now seems rather scrappy, the zig-zag is much more irregular and the silk looks fuzzy. It is just generally untidy. When you get to the last part of the “X”, it has degenerated into a mess. Now, please look at the third picture, which I borrowed from my Jan 4th spotting. You can see a huge difference in the quality of the construction of the web decorations. However, I realize that I could have got this all wrong. It is conceivable that the spider could have started the construction of its decoration at the messy part and improved as it progressed towards the tidy part, but I don’t think that matters. The end result is the same either way – a substandard stabilimentum. Nonetheless, all of the aforesaid pales into insignificance with the most important feature of this spider’s web decoration. Please see Notes.
This Signature Spider was spotted on its web this morning in the rice mill backyard. The web was moored to the stems of two banana plants.
When an adult female Argiope luzona constructs its web decoration, in the form of an “X” or even just a part of an “X”, it is called a Cruciate Stabilimentum. The linear sections which make up the “X” or “cross” are called “arms”. When the arms meet or intersect, at the hub of the web, they are called “Continuous”. If the arms stop short of the hub or do not intersect, they are called “Discontinuous”. So, the correct way to describe an Argiope web decoration would be, for example, a “Four-armed Continuous Cruciate Stabilimentum” (if the arms all meet or intersect at the hub) or a “Four-armed Discontinuous Cruciate Stabilimentum” (if the arms do not meet at the hub). Of course, the number just changes according to how many arms there are. So, there are One-armed, Two-armed and so on, up to Five-armed stabilimenta. The terminology makes it all very concise and unambiguous. So, what’s my problem with this spider’s decoration? In my second picture, a ventral view, the whole decoration can be seen. It clearly shows that the neat and sharp looking zig-zag does not reach into the hub and the diagonally opposite arm enters the hub, but does not quite intersect with the other arms. In the scientific article by a leading group of Philippine academics, Liza R. Abrenica Adamat et al. – “Salient Features of the orb-web of the garden spider, Argiope luzona (Walckenaer, 1841) (Aranea; Araneidae)” available from - https://www.researchgate.net/publication... it is stated that a “Three-arm stabilimentum may have two Continuous arms and a Discontinuous arm”. There is no mention of this mix of continuous and discontinuous in any of the numerous other configurations which are documented in the article. The study was conducted in a three hectare banana plantation in which 128 Argiope luzona spiders were observed.
Spotted on Mar 7, 2023
Submitted on Mar 7, 2023
8 Comments
Alright! You got to see the entire decorating process. Hmm thats odd there wasnt a flocculent puff of old silk at the webs centre - the remains of hte old web. Occasionally w my species A. appensa, it falls away on its own and once i saw a little silver thief spider Argyrodes cut it out and haul it away. Or maybe your species does things differently. Will just have to see, i guess.
Re the moulting spider, i think that it was the spider not the mantid that was the lucky one. After moulting shes a softie and so cant bite or fight. Shes lucky the mantid wasnt full grown or i think she woulda been lunch.
Also, in my experience, they only make stabilimenta before they moult, not so much after. Theres a paper by Nentwig who shows the same thing for A. argentata from Panama - so i think its a regular thing.
Re spotting 13, well done. Thats just how its been seen for A. argentata and my species: they always start from the outer hub and lay the arms down while moving towards the centre. A colleague of mine in South Africa sees the same thing with their common species, A. australis. So again i think your observations support that this is proly a widespread behaviour. A. appensa here seldom makes the full X, so that was nice to see A luzona do it. I think what will be really cool is if your species makes a Y or lambda-shaped stabilimentum or the rarest one of all, one consisting of just the two upper elements. What ive seen is they still waggle their backside and go to the bottom part of the web, they just dont lay down any silk before they then go up to the top to lay the upper arm. Curious if your species will do that too.
I have a collection of just about all papers ever written on stabilimenta. Id be happy to send whatever you need, if youre keen. Im here on Guam (we're neighbours!), and my email is alexander.kerr@aya.yale.edu; i can send you a list.
Hi alexander.kerr,
I don't know if you saw my spottings - https://www.projectnoah.org/spottings/38... and
https://www.projectnoah.org/spottings/12... The first one had no stabilimentum when I spotted it, but it had just moulted. So, as you mentioned, I thought it might be ready to make a stabilimentum. I did everything you suggested, early the next morning, but ended up with no web decoration. That was on March 18, but then I noticed yesterday afternoon that it had a it had a stabilimentum and I went out and watched it this morning. What happened is in the second spotting, mentioned above, but I am confused about the removal of the old web (which I think it eats) because this morning I watched as carefully as I could as it built its new orb web and at the end of the process, there was no sign of the old web. The problem is that I really did not see it removing/eating the old web. Any further advice advice would be appreciated. John B.
Thanks again. The information in your latest comment is the only part of all of this that I already knew. I was completely in the dark about absolutely everything else until you explained it so clearly. I am, as you know, planning to do one or two early morning sessions to try and see some of this Argiope behaviour and to give myself a better chance of success, I was intending to go out and locate a "target spider" which already has a stabilimentum, in the late afternoon/early evening. I figured this would help in two ways; First, I would see what kind of stabilimentum the spider had already made and I might see a repeat (or even an improvement) on the following morning. Second, there are a good many snakes in our area. So, I want to plan where I will be stepping as I approach the "target spider". I would not want to step on some poor snake in the dark and maybe suffer a bite in return. I know it sounds very melodramatic, but we have had a couple of deaths from snake bites in our barrio (village) in recent months. A little careful planning always helps. Best regards, and thanks again. John B.
Good luck. One more thing: Some individual spiders decorate alot, some never. Those that do tend to make them in bursts, like before moulting or making an eggsac. Thus, the best indicator that a spider will make a stabilimentum tomorrow is that they made one today.
Hi alexander.kerr,
Sorry for taking so long to reply. Many of my email notifications are arriving several hours late. I think my internet server is having problems. Once again I have to thank you for the wealth of detailed information you have given me. Now that I know what I have to do (and how to do it), I will get it organised as soon as possible. I think Saturday or Sunday might be possible. I will look around today and tomorrow, during daylight hours to select my target spider and then I will just do exactly what you suggest. If I do everything right and get a result, I will let you know immediately. It will be very interesting to find out if A. luzona does everything in the same order as A. appensa or if there are inter-specific differences in the procedure. I can't wait to get started. I have sometimes thought of specializing in Argiope spiders and I think I am getting closer to making that decision. I have read quite a lot about the various types of stabilimentum which are documented and I am sure there must be some more types/styles which have not yet been observed. However, it seems to me that the biggest gap in our knowledge of these web decorations is not how many types there are, but what is their real purpose. There does not appear to be a concensus of opinion on this and it may be that an answer will never be found, but I have one or two little ideas I want to think about and the more I can see, the more my ideas might develop, or end up in the trash can :-). Thank you once again. John B.
Hi John B,
Thats a great question. I am close by on Guam, so that time of morning is still dark for me, too. Web building here commences sometime between 0400 and 0500, with a few stragglers starting later. The whole web takes about 45-60 min to make and the stabilimentum if built takes about 30 sec and is installed as the very last step, so its easy to miss. Youll know shes getting close when shes finished laying the sticky spiral. She lays it from the outer web inward until her legs touch the webs centre. Then she stops, goes to the centre, eats the little blob of waste silk from the old web. This leaves a hole in the centre, over which she weaves some silk. Then she keeps up the side to side weaving motion as she walks down to the edge of the sticky spiral, turns, and begins laying the stabilimentum.
I use a flashlight to watch Argiope appensa make their webs. The light doesnt seem to bother them, they just keep on building their web, but i suppose each species might be different. The only occasional prolem is that the light sometimes attracts moths to the web and if ensnared cause the spider to pause web construction to bundle the prey and, if its quite small, eat it. They then return to web building. However, if the interruption occurs during the laying of the stabilimentum, she may not finish building it. So for example, she may only build a short upper arm when, had she been undisturbed, she might have put in a longer one.
Hope this helps. Lemme know how you go. After a few days of getting up at 0400 youll soon see why literally no one has ever bothered to observe how the stabilimentum are actually constructed! lol
Hi alexander.kerr,
Thank you for your comment. The information you have given me is going to be so helpful going forward. There is, as I am sure you know, a great deal of information available online about Argiope spiders, but I cannot recall any article which provides the kind of detail you have just laid out in two short paragraphs. I can see that I must get out there early in the morning, as you suggest, so that I can see what you have just described. I feel that there is so much to learn about these spiders and for some time, I have been considering devoting more time to them. I don't want to pester you, when you have already been so helpful, but there is one point that might be important. I don't know if there is already daylight at 4:30 a.m. where you live, but here, in Philippines, it is pitch dark until about 5:15 a.m. I would have to use a flashlight which might cause the spider to behave differently. My question is; "Does the spider start when it is still dark, or does it start just as dawn is breaking?" Sorry if it is a stupid question, but everything is difficult when you just don't know. I hope you can spare a moment to answer so that I can plan my next observation of these wonderful spiders. Thanks again, John B.
Great observation John B. Ive watched Argiope appensa make their stabilimenta, which they usually make around 0430 to 0500 h in the morning. They always start from the bottom, working their way to the centre. Then they walk over to the top and write another arm of a diagonal, also from the outer portion to the central part. So, it would seem that your spider made the neat lower portions first.
Your notes on discontinuous stabilimenta is also interesting: They make each diagonal separately and so can i guess decide whether each one or both will be continuous or not. I hope youll continue observing Argiope and get to see them construct them early in the morning.