Sunday, September 4, 2011

Spider Sunday: Black and Yellow Argiope

The Facebook page for SpiderIdentification.org is really busy these days. It is no surprise. Spiders in the northern hemisphere, especially orb weavers, are reaching maturity now. Larger spiders spin larger, more conspicuous webs, often in situations where people notice them more often. The chief attention-getter in the United States right now is the Black and Yellow Argiope, Argiope aurantia.

The females are very large spiders, with a body length of 19-28 mm. Their bright Rorschach pattern of black and yellow might set off your “dangerous arachnid” radar, but no orb weaver of any kind is considered by scientists to be dangerously venomous to people or pets. Males, by contrast, are tiny, only 5-9 mm in body length, and magnitudes smaller in terms of body weight. Females need to build up energy reserves to be able to produce eggs.

The female Black and Yellow Argiope spins a rather small orb web given her size, usually in tall grass or shrubs no more than two or three feet off the ground, and usually lower. There, her snare can intercept large insects like grasshoppers.

A distinctive signature in the webs of most Argiope species (there are at five species north of Mexico) is a thick, zigzag band of silk running down the center of the web. This structure is called a “stabilimentum,” and its function remains something of a mystery. It may serve to shield the young spiders, which confine the stabilimentum to the hub of the web, from harm. The young spider quickly zips to the other side of the web when it feels threatened. Another hypothesis is that the stabilimentum is like a beacon on a tall building: it advertises the presence of the web to birds in flight so that the avian animal won’t destroy the web by accident. This comes at a cost, however. The presence of a stabilimentum can reduce prey-catching success by as much as thirty percent (Blackledge and Wenzel, 1999). That statistic also flies in the face of yet another hypothesis: that the stabilimentum most likely functions as a lure. The silk band stands out bodly in the ultraviolet end of the light spectrum, and many insects seeking flower nectar may mistake it for a raceme of flowers. Not all individual spiders spin a stabilimentum, and one might assume that webs spun higher in the vertical plane would be more likely to have one if the purpose was to deter bird strikes.

Look for male spiders lurking on the outskirts of a female’s web. They may be attracted to the female by a pheromone she emits (Olive, 1982). Approaching cautiously, a male may eventually be able to couple with the gargantuan object of his affection. He inserts one of his pedipalps into one side of the female’s epigynum (female external genitalia), and quickly pumps his sperm into her, hopefully before she renders him a meal. He will repeat the process with his other pedipalp on the opposite side of the female’s epigynum, if he is able. Should he succeed even once, he usually breaks off the tip of the pedipalp, which remains stuck in the epigynum. This “mating plug” therefore prevents any competing male from inserting into that opening (Foellmer, 2008).

Once mated, a female produces one or more egg sacs, each about the size of a large marble, and covered in tough, papery silk. Inside are 300-1,400 eggs. The eggs hatch in late autumn or early winter, but the spiderlings do not exit the egg sac. Instead, they go into diapauses, a dormant state with lowered metabolism. They emerge the following spring and reach adulthood by late summer. Various parasites and predators can take their toll on the egg sacs and spiderlings, however. One study found that 19 species of insects and 11 species of other spiders emerging from the egg sacs of Argiope aurantia. Chief among the parasites were the ichneumon wasp Tromatopia rufopectus, and the chloropid fly, Pseudogaurax signatus. The overwhelming predators of the egg sacs are birds. Nearly every egg sac found in the wild during the study had suffered damage from birds (Lockley and Young, 1993).

The Black and Yellow Argiope is also known as the “Writing Spider,” named perhaps for the stabilimentum, Golden Orb-weaver, and Yellow Garden Spider, among other aliases. I grew up learning it as the “Golden Garden Spider.” The species ranges from coast to coast in the United States, but is absent from arid regions.

Enjoy your encounters with these remarkable spiders while you can. The first frost is likely to claim their lives, if they do not perish in some other way before that date. See if you can determine what kinds of insects they are preying on, and whether their web location changes. There remains much to learn about even our most common and conspicuous arthropod neighbors.

Sources: Blackledge, Todd A. and John W. Wenzel. 1999. “Do Stabilimenta in Orb Webs Attract Prey or Defend Spiders?” Behavioral Ecology. Vol. 10, No. 4, pp. 372-376.
Foellmer, Matthias W. 2008. “Broken genitals function as mating plugs and affect sex ratios in the orb-web spider Argiope aurantia.” Evolutionary Ecology Research. Vol. 10, pp. 449-4462.
Lockley, T. C. and O. P. Young. 1993. “Survivability of Overwintering Argiope aurantia Egg Cases with an Annotated List of Associated Arthropods.” Journal of Arachnology. Vol. 21, No. 1, pp. 50-54.
Olive, Cader W. 1982. “Sex Pheromones in Two Orbweaving Spiders: An Experimental Field Study.” Journal of Arachnology. Vol. 10, No. 3, pp. 241-245.

48 comments:

  1. Awesome post as usual, thank you! Again, you had some bits I didn't know.

    The only time I've seen Argiope make webs up high was at a horse farm, and there were many Argiope 10 to 30 feet up around the stables. I recall a naturalist at McKinney Roughs Nature Park in Texas telling me about a bird (I forgot what kind) he saw day after day pluck Argiope straight out of their webs, just feet off the ground. I have seen adult Argiope switch sides of the stabilimentum if I surprise them, so I'm betting that it's a protective scheme. It's pretty impressive to see a large spider magically switch sides of a web.

    In addition to the names you gave, kids here also call this spider the Zipper Spider and the Banana Spider.

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  2. Thank you so much for sharing your own observations, experiences, and knowledge! That is exactly what I want to have happen on every blog post. I sure don't know everything!

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  3. This is one spider that I actually find so interesting. It's that web they make! Fascinates me every time I find one. Plus the spider itself is so colorful. Even for someone as 'arachnophobic' as me.

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  4. Aloha -
    Completely lost my writing about our Argiope appensa on Maui to log in to WP. So here we go again...
    Like Spider Joe observed, these big gals scoot to the other side of their webs very fast. They are very shy when humans get too close. The boys hang out for a very long time on their side of the web, nomming on the foods their gals provide.
    They tend to like more moist/humid sections of the island, rarely found in the leeward/dryer areas.
    Their egg sacks look like small 1/2" dirty bits of white cotton candy. Stuck off of one side of the web.
    Thanks for sharing all your knowledge, Eric. I am aware of you from your help with Daniel at WhatsThatBug.com.

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  5. About 2 weeks ago, I saw my 1st Argiope at the bottom of my deck steps - and she was BIG - at least a full 2" long, legs extended. Every morning I went out and checked - still there, about 12-18" off the ground in the middle of my oregano. This morning, I go out to check on her and either she 'shrunk' (ha ha) or the big momma is gone, and something that looks exactly like her, but about 1/3 as big is there in her place... can you shed any ideas about what happened? I have several photos if you think that would ever help...

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    1. You probaly saw the male. I have one on my deck (female with 2 egg sacs) and I spotted the male on his web down about 3 foot away from her at the bottom of the deck. Pretty cool.

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  6. Hi, Sandy. Probably the same spider. I'll bet she laid an egg sac. Maybe you can find it somewhere off the perimeter of her web. She was gravid before, now she has to gain weight again :-)

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  7. funny you should say that, because I had gone out a few hours ago to look at her again and thought - was she that big with an egg sac? I read somewhere else that the sacs looked like "balls of cotton fluff" on the perimeter of the web - maybe they were describing a different species? I'd love to send you the "diet" pictures...(before and after...) - lol!

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  8. My Argiope "Charlotte " laid an.egg sac right by the door of the walk-in cooler at our produce market. I loathe spiders in general, but her boldness caught my attention, so once we googled her, i decided we needed to keep.her around to observe! She has laid 2 of.these sacs, and although i haven't seen the male, I'm sure he is around! I keep showing her to all the kids who visit our market. Very much a.learning experience! Thanks for all the interesting info!

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    1. Jenni! Thank you so much for sharing your experience and observations. We *love* to hear stories like this :-)

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    2. Hi Eric!! My kids and I have been watching "broomhilda" for a little over a month now. She has made a home right outside our living room window. I have noticed just over the past couple of days that there is now an egg sack. I was wondering, after she is gone, would I be able to take a stick and maybe wrap the web and egg sack and put it inside a butterfly habitat and bring it into the house until they leave or will the temperature difference affect the babies?

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    3. Hi, Gina! I think you could probably bring the egg sac indoors. I'd vote for pruning whatever it is attached to rather than cutting the sac out of its moorings....I don't think temperature has much effect on when the egg sac would hatch, but do put it in a place that is exposed to natural changes in day length. The little ones won't emerge until late next spring.

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  9. Our argiope laid two egg sacs weeks ago, but they have since disappeared. Predators, perhaps? "Mama" has survived one frost and remains in her usual web next to our front stoop. I have truly enjoyed watching her this summer; she even consumed stink bugs! I'm hoping she survives hurricane Sandy...

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    1. Thank you so much for sharing your experience, Susan! I *love* to hear stories like yours :-)

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    2. Two eggs sacs located on the playground fence at our school... ACK! Relocate? Exterminate? or Science Project?

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    3. Ivy: Apologies for the delay in replying....You don't state where the school is located geographically, or describe the egg sacs. If they look like the one pictured here, and are large, then no need to do anything at all. Black widow egg sacs are white, more pear-shaped, and usually not out in the open. They are smaller, too.

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  10. I may be too late with my question (since I notice there hasn't been activity here in almost a year). We've had an influx of these spiders around the school lately! More than normal rain, perhaps, dunno, Anyway, we located two rather large egg sacs on our playground fence. We've observed one of the sacs moving **CREEPS** ... should we relocate the sac? Is it safe to have it around children? My vote was to destroy it (sorry). But other teachers and children want to continue to observe it. What to do?

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    1. Without seeing at least an image of the objects you are describing, I can't even tell you whether they are spider egg sacs. Suffice it to say they certainly pose no threat whatsoever. Let the kids observe, but it would be prudent to teach them not to touch wild animals of any kind, unless in the company of an expert.

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    2. I have had the Argiope in my gardens for 20 years.
      I have moved to a new location and they do not exist here yet.
      This may offend some but does anyone know of a source for obtaining an Argiope egg sac so I can introduce them to my new location?

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    3. Well, there may be a good reason they do not live where you live now, even if we don't know what that reason is. There would probably be marginal survivability (if any at all) if you tried to introduce them. I don't find your idea offensive (you aren't talking about a potential pest), just unlikely to be successful.

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  11. I know have three Argiope in my yard right now, and I think I've had a total of that many in my yard in the preceding 8 years. I've been trying to understand why. I can think of two possible explanations: (1) We've had frequent rain this year, contrary to most preceding years; and (2) I've been gradually transforming my yard into 1/3rd acre of wild land, and this is the first year it's nearly all been wild. I'm wondering if maybe the conditions have been right in my yard for every instar of the spider. They start out small and eat small things. As they get bigger, they need to eat bigger things. My yard now offers it all. Once Argiope get beyond a certain size, I doubt they can move very far. Or I could just have a lucky year.

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  12. We have a VERY large female argiope living under the eaves of our back porch. We're about to have our house painted, and I'm wondering about the possibility of relocating her. Oh, and 3 egg sacs. I don't want her or her progeny to be casualties of our home improvement.

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    1. Relocating the egg sacs to a protected place should be no problem. Same with the spider, though she may be nearing the end of her life anyway.

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  13. Thanks for the info! We sort of ended up adopting a yellow garden spider that managed to make it's web inside our screened enclosure, even to the point of providing crickets for it as we weren't sure it'd get enough insects inside the screen (but weren't sure how to relocate...) Anyway, the spider is gone and presumably passed, as fall is getting close, but she did leave an egg sac. My plan (such as it is) is to leave the sac where it is, protected, for most of the winter, then move it to the outside garden before the young come forth. The idea was this would limit exposure to predators... Is this a good plan? Any advice about when to relocate, or how to relocate, or what sort of environment/place we should relocate to? We're in Pensacola, so temps probably won't get all that cold, and live on the edge of a wooded area so should be able to find a fairly good spot for the egg sac, but would certainly appreciate some advice on how to go about this... (Oh, and the sac is on the web, attached to the pool screen, so I won't be able to simply prune a twig or something to remove it; I'll have to actually take the sac on it's own...)

    Any help you could offer would be appreciated. We'd grown attached to our adopted pet, though we knew from reading she wouldn't last longer than a season, and would like to get the little ones to somewhere where they'd have a chance to flourish (though not, ideally, inside our screen! We prefer them out in the yard!)

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    1. That's a tough call. I might suggest that you pose this question to the website "Arachnoboards," or on one of the many Facebook groups dedicated to arachnid appreciation. I simply don't have enough experience in this to offer sound advice.

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    2. Hello Eric. Stumbled across your blog searching for answers and promptly bookmarked it. We always have two or three of these lovely creatures in our garden but there's always one who sets up housekeeping near the ceiling under our carport. She expired a few weeks ago. Thanks to a garden cam, we discovered her immediately and she now resides in a jar on my desk (sounds morbid, I know, but she was much loved).

      Meanwhile, we've had some bad weather here and her egg sac went missing. Husband located it where it fell and rescued it...brought it inside. Not good. For the past 2 yrs we've had one in an abandoned birdhouse which resides next to our patio under the eaves. There are no egg sacs there now but I'm thinking this is a safe place as we've watched egg sacs hatch in that location for two years now. What's your opinion? If it's viable, we want to give it every chance. It's there for now but if we need to relocate it, we will.

      Thanks in advance for any direction you can offer. Oh, I should say, we are in middle Georgia.

      blessings,
      ~discerning

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    3. The birdhouse sounds like an excellent idea. Once the spiderlings "hatch" in early summer, they should be able to easily find the "exit" and then disperse by ballooning. Thank you for sharing your story!

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    4. Thanks for the quick reply. I can breathe a sigh of relief now. The birdhouse is a long-ago-seen-better-days number my dad & I built together many years ago which is why it's located where it is now. When he passed away, I confiscated it and put it in a protected area under the eaves here. The bluebirds loved it in its heyday but it will henceforth be known as Charlotte's House aka The Spider House - courtesy of the kid's when we moved it. The top is actually open an inch or so as the hinges have rusted in that position. Turns out, silly sentimentality paid off in this case.

      I'm enjoying your new-to-me blog and will report back when our youngsters hatch. Now I'm off to get the hubs to relocate that garden cam so we can keep an eye on them. What fun!

      thanks again,
      ~discerning

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  14. I found one of these about 3 feet from our front door and called my son who is scared of any spider. He got a laugh from watching me touch her back. I quickly removed my finger after gently touching her to prevent ripping her web. In a flash she was on the other side of the web ,still in the center and making the web bounce like a kid bouncing on a trampoline without leaving the mat.

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    1. Thank you so much for sharing your story and observation. Exactly how they do that maneuver is beyond my comprehension.

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  15. So I have one of these marvelous spiders right outside bedroom window. I am very afraid of spiders but I know that this one won't bother me. We have named her francine. Is there any chance she will come in my house? If so is there a way I can relocate her?

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    1. Wonderful story! No way will she come indoors. I've never heard a single story of that happening, and she is wanting larger insect prey than she would likely find indoors. :-)

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  16. I have a ridiculous fear of spiders of all shapes and sizes. My young daughter, however, swears she will be an entomologist someday. A few weeks ago we found an argiope in my veggie garden. She's one of the biggest I've ever seen and absolutely gorgeous. Despite my anxiety, I have let her stay and my daughter and I visit her daily. Only problem is getting to my ripening tomatoes right behind her web. They may have to be a sacrifice for the greater good.

    Bug Mom

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    1. Wonderful story! Don't worry, the spider will run to a corner of the web, or drop to the ground, if she's unduly disturbed. She'll go back home once the "threat" has passed.

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    2. I have a beautiful lady at my house Named Talula.. have egg sac on my porch and I am afraid the babies will end up in my house. My logical side is saying no, they will balloon out. The sac is stuck to my ceiling and I am afraid I will damage it when I relocate. Another thing do the mothers always leave when they die? I feel mine died last night but she is in a very dramatic pose.

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    3. Anonymous, 9/29/16: Yes, the spiderlings should balloon to disperse, but they often huddle together for a time before they leave. The female spider may die in her web, yes, though I usually find the egg sacs with no mother spider in sight.

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  17. Hi Eric, I have stumbled across this blog while looking for information on the garden spiders egg sac. Every year we have black and yellow garden spiders that build a web in bushes by our front door. These spiders have a zig zag pattern in their web. Today i noticed an egg sac attached to the gutter nearby. My queston is this. Do I leave the sac or remove it? I have read that it may hold as many as 1000 eggs and I really don't want that many spiders nearby. Any suggestions?

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    1. Once the spiderlings emerge, they will quickly disperse by "ballooning." You won't have that many spiders in your immediate vicinity.

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  18. We have been watching a lovely spider for the last month. She built her best under our covered porch by the light. We named her "Charlotte" (of course) and have been checking on her daily.

    We are scheduled to have our porch screened in within the next week or so.

    She just made a beautiful egg sac just where we need to screen!

    Is there any way we can move her eggs somewhere safe? I really want my porch screened in, but we are also worried about our spider friend!

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    1. Hi, Lauren. Thank you for your concern for the spider. You could probably snip the "anchor threads" attaching the egg sac to the porch. After that maybe affix it to an unused broom or something leaned against some other sheltered spot? The egg case insulates the spiderlings from cold and such, but wind would be a problem unless you sheltered the egg sac somehow.

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  19. Hi Bug Eric,
    We have had a few of these spiders on our back porch. One is still alive and she is up to her third sac of eggs. However we are up to 7 sacs of eggs on our back porch. I was reading through some of these blogs and wondered if anyone had issues with relocating? I def. do not want a possibility of having a few thousand spiders on our back porch although I know they float off with a web, but still a little eery. The spider is cool. She actually showed up right after I had surgery and was home for 2 weeks. I watched her get fat 3 times already wondering if that will be it. Ha.She is under our porch light close to the back door handle. I threatened everyone to not touch. We do not like spiders but once she showed up I googled her and found out she is fine. So she catches plenty of bugs all night. Rebuilds her web in the morning after cleaning it up. It is very cool. I have enjoyed her. I just want to get those egg sacs off the porch by spring. Without harming them..��

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  20. I love these spiders. We've had at least one for the past five years at my house. Each one is named Charlotte lol. So our last one had 4 egg sacks (whore) lol. And I got to watch her and did a Facebook live on her filling and wrapping her egg sack! AMAZING!Going to try and carefully put a sack in an old decorative bird house for my dad. He loves them two. He hasn't seen them at his house in years. I might move another two in bird houses for me back yard and leave one. They are awfully exposed on a fence post.

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  21. So a bird house is my best bet. I love the spider too. I have enjoyed her. I think she is about die. Makes me sad actually. I named ours Sophia, I didnt want to abuse the Charlotte name. Ha 😁

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  22. Hello, I'm hoping you can help with a specific relocation technique for someone who is not a fan of spiders but really things this one is special. Last night a LARGE female spun a web on our porch, but unfortunately one of the webs anchors is our radio flyer wagon. Any tips on how to move her to the garden?

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    1. Oh, shucks, just break the wagon free. She has to rebuild the web every time she catches something anyway. She'll find another place to anchor or build.

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  23. Eric, I'm hoping you can help with my question. I love these spiders and have had a female each year, in the same spot on my back deck. The female has put her egg sacks in a very bad spot on my house eave where the winter snow/ice will slide and drop taking the egg sack with it. I was horrified to have found this happened the first time a female left her egg sack in this spot. What would you do?

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    1. I generally discourage intervention in cases like this. Nature is able to cope with most situations. Wholesale habitat destruction is one thing we should *not* tolerate.

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  24. we have two large female ( writing spiders ) about 3 feet from each other on our back deck. we have a 3 foot potted tree with an egg sac in it. we bring the tree in for the winter. i'm thinking of cutting the few branches around that are supporting the sac. but do not know where to put it for the winter. any ideas would be grand. my name is Patrick. Thanks bug eric for your informative blog.

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