Male and Female Yellow garden spiders in Texas 5

— This article by Jerry Cates, Pete (Spring, TX), Amy P. (Ponder, TX), and Joy R., first published on 25 January 2011, was revised last on 18 August 2013. © Bugsinthenews Vol. 12:01(09)

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The yellow garden spider (Argiope aurantia) is a common sight in mid to late summertime yards, gardens, and woods throughout the contiguous 48 United States. The female is marked with black, yellow, and white on the abdomen, and silvery hairs on the carapace. Males are much smaller, with less dramatic colors and markings; because the males die spontaneously at the terminus of the mating ritual, they are rarely observed beyond midsummer (but see CASE 07292010, below, for excellent images of a male observed in San Antonio in late July, 2010).

The genus Argiope is discussed in a separate article.

Pierre-Hippolyte Lucas (1814-1899), a French entomologist, first described this species in 1833, applying to it the specific epithet aurantia. The name derives from either of the Latin words aurum, “golden,” or auranticus, “orange-colored.”

Female yellow garden spiders tend to remain within a limited, localized area throughout their lifetimes. They construct elaborate orb webs, with bright white stabilimenta in their hubs. The webs are oriented in the vertical plane, and are effective snares for flying insects. In areas with abundant prey, these spiders grow quite large, inspiring awe and fear in those who come upon them on the trail, especially on watching the speed at which they swathe and kill the insects that become entangled in their webs.

These spiders are capable of biting — even through light clothing —  if handled roughly, or if accidentally captured between their webs and one’s body (as can happen when one by happenstance walks into a web strung across a trail). Though the bite can be painful, the venom is not considered dangerous. Allergic individuals may suffer unusual complications, however.

Individual case histories, provided below, supply additional details on the anatomy and life histories of these spiders.

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Amy wrote on 15 August 2010:

Jerry:

This fine lady has been on my porch for about three weeks. She just re-located her web on a window which gives me great view. Notice that she has a baby in the web with her. I’m so enjoying her – she is absolutely beautiful. The photos don’t do her color justice.

Amy P.

Ponder TX

Amy’s surname has been shortened to protect her privacy.

I hastened to let Amy know that the “baby” she had photographed on the web with the fine female yellow garden spider was, in fact, a male.

We don’t often see males on these webs, as most mate and die early in the season. Here, as late as mid-August, a male had taken up residence of the web with this female.

As with Joy R., whose yellow garden spider encounter is chronicled below — and who was actively photographing her yellow garden spiders, male and female, at the same time — Amy enthusiastically took up the task of recording and observing the lives of these spiders for the viewers of BugsInTheNews.

We thank both of these ladies heartily!

The photos sent in by Amy are posted as thumb nails in two groups. Group I is above, and shows the images dated 15 August 2010.

That group of nine images shows, in the first five shots (plus the first image at the head of this Amy’s report) a small, live male, with a much larger live female.

Both are at rest in these images, with the female at the center of her web, and the male — on the other side of the orbal plane — positioned directly behind her.

This would place the male essentially out of sight.

On the other hand, the male would not be “hidden” in the fullest sense of that word, as any movement by the male would transmit vibrations in the web to the female, who would be able to use those vibrations to track the male’s position very precisely. Because of this, it must be presumed that this female has chosen to tolerate the presence of this male, for otherwise the latter would either be chased off so aggressively as to cause it to find another place to stay, or would be stalked and eventually killed. Tolerance suggests receptivity to mating, and it seems likely that this male has sensed that receptivity, and is now biding its time, awaiting the proper moment when mating would be most propitious.

In the last four images in this first group of photos, we see the female wrapping and biting a grasshopper, after the latter had flown into the web. The male could not be seen in any of the full sized photos from which these images are taken, even on the periphery of the web. That is expected, inasmuch as the female is not safe to be around when attacking, swathing, and killing prey.

In the second group of images, we see the male, now dead, and are able to examine the condition of the male’s palps.

From these photos we see that the dead male has not been attacked by the female, as the corpse appears to be in intact.

The palps, on the other hand, show signs that they have been used in the act of mating.

Also, though the left-hand palp is intact, the right-hand palp shows signs of damage, with — according to my interpretation of the images — the embolus caps of both palps now missing.

That evidence suggests strongly that both palps were inserted into the female’s genital tract, that the left-hand palp was inserted first, and its embolus cap was left behind when the palp was withdrawn. Then, generally after a period of re-courting behavior, the right-hand palp was inserted next, at which point the male suffered a fatal cardiac arrest en copula, before that palp was withdrawn.

The embolus cap of the right-hand palp would have snapped off the moment the palp was inserted, and additional damage would have been done to the embolus itself, when the female detached the male’s corpse from her body. The embolus caps would have effectively plugged both sides of the female’s genital tract, as described by Foellmer (2008, Adelphi University, N.Y.), in his paper on this subject. This has the effect of preserving the priority of this male’s sperm, i.e., protecting its paternity, by preventing another male from mating with this female.

It is of interest to note that mating took place just prior to the female’s deposition of eggs. Amy reports that she saw the male alive the evening of 30 August, but on the morning of the 31st the male’s corpse was found on the web, and the female was observed preparing an egg sac.

Amy is hopeful she will see this spider’s offspring in 2011. She wrote:

Jerry:

It’s great seeing these photos on the Internet! She made a third egg sac and then passed away shortly after that – I would guess by mid Sept 2010. I do miss her and appreciate the enjoyment she gave us. The egg sacs were relocated to our front flower bed. I look forward to seeing her offspring in the spring. Maybe we will have another set of photos for you.

Amy

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Joy wrote on 29 July 2010:

Hi, Jerry.

Here’s a nasty “little” guythat’s on my porch. He looks scary.He also looks like he has some massive teeth. What is he?

Thanks, Joy R.

Note that the photographs posted on this page, as with all the photos posted on bugsinthenews.info, can be enlarged for more detailed viewing by placing your cursor over them and left-clicking.

The photos posted here are not ordered precisely as Joy sent them in, but each is dated in its caption.

The first set of photos, referenced in the email of 19 June, were of a mature female yellow garden spider (Argiope aurantia), all alone on its web,  that Joy had photographed that morning. We know this female is sexually mature because, prior to the last molt, the carapace (the hardened anterior portion of the body, distinguished from the softer posterior abdomen) is marked with dark radial bands not observed in Joy’s specimen. After the last molt the carapace  is entirely covered with silvery hairs, rendering the carapace essentially unmarked.

The “massive teeth” Joy referred to are not fangs but diminutive, jointed appendages, in front of the spider’s face, called pedipalps; females use them to examine prey prior to feeding, and to manipulate prey for mastication. For that reason the female’s pedipalps (shown in the two photos below) are uncomplicated, leg-like structures covered with innervated hairs. The male’s pedipalps, by way of contrast, are tipped with specialized structures (emboli) that are used as reservoirs for sperm prior to mating, and that effectively discharge the sperm into the female’s epigynum during copulation.

I asked Joy to think about taking additional photos to chronicle the spider’s life, preferably all the way to where the female would produce an egg sac. The yellow garden spider is the most beloved of our North American garden spiders. It is quite small in the early spring, after emerging from the egg sac produced by its mother the previous fall, but in the presence of abundant prey the females grow quickly to enormous size, entertaining us throughout the summertime with their awesome beauty and the powerful ways they capture, swathe, and consume insects and other animals that are unfortunate enough to be snared in their webs.

Juvenile females spin individual webs and begin capturing prey. After molting several times, the female arrives at the penultimate state of development, just one molt from sexual maturation. At that state, males often congregate on or near the web, awaiting the next molt.

One or more of these males will successfully mate with the female in the midst of the ensuing molt, when — because she is immobile — they are not at risk of being attacked. This is important, as studies have shown that males who attempt to mate with mature, mobile females face a high risk of attack, and are often killed before mating can be consummated. Having previously filled the bulbs of their pedipalps with sperm, they insert one of these into the female’s epigynum, then — by increasing the pressure of the blood supply (hemolymph) to the palps — sperm is discharged into the female’s seminal vesicles, where it is stored until the eggs are fertilized.

Matthias W. Foellmer (then at Concordia University, Montreal) and Daphne J. Fairbairn (University of California, Riverside) published a study (2003, Spontaneous male death during copulation in an orb-weaving spider) that described this process, and its curious aftermath.

It happens that, for this particular species, the male expires soon after its second pedipalp is inserted. Evidently, the mating male suffers a cardiac arrest triggered by the physiological processes associated with  discharging sperm from the second pedipalp; his dead body remains attached to the female’s underside until she takes steps to remove it. Foellmer published a later study (2008, Adelphi University, N.Y.) showing that the male pedipalp often snaps off as his body is removed, effectively plugging the female’s epigynum and protecting his sperm from competition by future males.

Virgin males that fail to copulate with females during the final molt continue to search for females, though before long their chances of mating opportunistically (as copulations with molting females are termed) become nil. These males, however, refuse to accept a life of celibacy, and — whenever possible — seek out and attempt to mate with fully mature females, whether the latter have mated previously or not. The male photographed by Joy is one of these spider-come-lately fellows. As the photo shows, the male’s pedipalps are intact, and this plus the very fact the spider  is alive suggests strongly that it has not copulated successfully in the past.  In Foellmer’s 2008 study, he provides a photo of the male pedipalps, which may be compared with the photo provided here.

In either case, whatever sperm is deposited in the female’s epigynum is stored in internal spermatotheca, and weeks or months later are used to fertilize the eggs as they are discharged from the female’s body, into an egg sac of the female’s manufacture.

Shortly after producing, and filling, the egg sac, the female  dies, as the species doesn’t usually overwinter in the adult stage. My hope was that  Joy would photograph the sequence of events as it unfolded, and though she wanted to comply with this request, there was a problem:

The spider had built its web in the worst possible place, on the porch precisely in the way of traffic. Although she and her husband had no children, they did use the porch, and having the spider there would be a serious inconvenience.

We then discussed how the spider dismantles its web every night, and rebuilds it just before daybreak. If incentives could be provided to entice the spider to move to another location, chances are it would take the hint.

Most likely it was on the porch because the outside porch light was left on all night long, which attracted bugs and kept the spider busy at night as well as during the day.

Turning the porch light off would cut off that source of food, and that ought to make it  choose another place to build its webs.

Joy turned off the porch light, and before long the spider dutifully moved to her flower garden, nearby, where flying insects were now more plentiful. There, the spider was no longer in the way of traffic, and Joy could take photos to show how it was developing.

Joy took additional photos on July 29, and sent them in, mentioning that the spider’s mate was on the web with her.

The first photo posted on this page shows both of them, together on the web, the relatively large female on the side of the web closest to the camera, the correspondingly diminutive male on the other side of the web.

Notice that the male is positioned back on the web relative to the female, with its body oriented so that she cannot visualize the male’s body, although the male’s front legs are in view. In all the photos Joy took, this stance was maintained. It is likely that this position reduces the risk that the male will be attacked by the female. Note the enlargement of the underside of the male.

The egg sacs produced by a single female number from one to five, and are constructed in late summer or during the fall.

Each sac is a leather-like pouch that contains up to 1,000 eggs and measures from 5/8-1.0 inch in diameter.

In the photos Joy sent, we can see both the structure of the egg sacs themselves, and the silk scaffolding that the female usd to fix their positions in space. Scaffolding stabilizes the egg sac against buffeting by wind, rain, and other natural conditions that, under extreme conditions, can destroy the egg sac and its contents. Since the offspring of spiders that take time to secure their egg sacs with scaffolding have a greater chance of survival, scaffolding can be seen as an adaptation for which evolution selects.

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Questions? Corrections? Comments? BUG ME RIGHT NOW! Feel free to e-mail me at jerry.cates@bugsinthenews.info. You may also register, log in, and leave a detailed comment in the space provided below.