Spiders at Brazos Bend 5

SPIDERS -- PAGE 5 Orb Weavers (besides Nephilas)
This page was born 09/13/2004. Rickubis designed it. (such as it is.) Last update:
Images and contents on this page copyright © 2002, 2003 Richard M. Dashnau

Here are some of my other Brazos Bend pages:
Spiders page 1
Spiders page 2 (Nephila clavipes)
Spiders page 3
Spiders page 4 (Jumping Spiders)
Spiders Page 6(fishing spiders)

This is my third page of information I've found about spiders. Most of these pictures were taken at Brazos Bend State Park. I hope that, like me, the next time you see a spider (and they are almost everywhere), you'll take a second to admire their form and function.

March 16, 2003 Okay. I'm sure that repeat visitors to the RICKUBISCAM are wondering: "Rick? What about the SPIDERS?"
Well. For one thing, it's still actually winter. But, here on the RICKUBISCAM page, that doesn't matter. Last Wednesday, I noticed something that was apparently floating above my dining room table. Closer inspection showed it to be a spider--in a web! (See 8- LEGGED WINTER VISITOR, below). Well, of course I had to take a few pictures. After all, it's not every day that an orb web appears over your table. My visitor appears to be a "Garden", or "Cross" Spider. (Araneus diadematus.) While I was looking at the spider, it started moving around the web (see WEBWALKING, below). Meanwhile, I was trying to focus on it, so I could use the picture to identify it (see ANOTHER SHOT, below). Identification was difficult, since the spider's markings and appearance were hard to see. Why? Well, the last picture (RICK AND THE VISITOR, below) shows the tip of my index finger with the spider, for scale. Kind of difficult to see, wouldn't you agree? Since this photo session, the spider has moved on.
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8-LEGGED WINTER VISITOR WEBWALKING ANOTHER SHOT RICK AND THE VISITOR

April 06, 2003 I've been watching the trails for signs of new spiders. Finally, as the pictures below (YEP, THAT'S SMALL shows, I found some.

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                             YEP, THAT'S SMALL
It was very difficult to tell what kind they might be. The object in the lower left of the picture is a QUARTER! That's right, a 25-cent piece. That's a pretty small spider! I hoped that these might be Golden Silk Spiders (Nephila Clavipes), but it's too early for those to appear. They might be Black and Yellow Argiopes (Argiope Aurantia) though. Here are more pictures of them (see below). There was just no way to tell what kind of organism the spiders were eating (see WHAT'S IT EATING, below). That image also shows the spider's underside. The webs, at first glance, seemed to be random collections of strands, but closer inspection showed that there were orb webs (about 2 inches across) in amongst the strands. I didn't notice any obvious stabilimenta (those zig-zag patterns that argiopes make in their webs), either. A comparison of two pictures (WAITING FOR FOOD--taken 04/06/2003, and ADULT ARGIOPE--taken 7/14/2002 ) shows some possible resemblance in the color patterns, but the physiological details are just too small to see and compare.
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WHAT'S IT EATING?   DON'T NEED MONEY!   WAITING FOR FOOD      ADULT ARGIOPE          QUARTERBACK

Why don't spiders get stuck on their own web when they walk on it?
Spiders have 8 "walking legs". These each have 7 segments. The picture below (BIG TROUBLE) shows the last of these segments, the tarsus. (in order from the outer end, the segments are: tarsus, metatarsus, tibia, patella, femur, trochanter, and coxa; click on the LEG SECTIONS image below to see 640 x 480 image). All spiders have claws (two or three) at the end of the outermost segment (see CLAWS FROM THE SIDE, below). The Nephila Clavipes (and other spiders who hunt by using a hanging web), uses an interesting method to walk on its web. The two "main claws" (which have serrations on them) are not used for this at all (see CLAW FROM UNDER). Instead, there is a smaller, smooth claw between these two larger hooks. Look closely at the first two pictures, and the RICKUBISCAM, and you'll see that the large claws are not holding the web at all.
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BIG TROUBLE LEG SECTIONS CLAW FROM THE SIDE CLAW FROM UNDER
This claw can fold in and back out. There are also two stiff hairs alongside this claw. The spider, when it wants to grasp its web, puts the web between the folding claw and the two hairs, so the hairs are on one side of the web, and the claw is on the other. The claw then folds in, and presses the strand of web against the two hairs. This pressure slightly bends the web across the hairs, and allows the spider to hold onto it. To release, the spider relaxes the muscles which pull the hook, and the web springs back out. The next time you see a spider walking its web, note how only the very tips of its legs touch the web.
As I've noted before, I've used: The Biology of Spiders, by Rainer F. Foelix, published in 1996, as a reference.

August 07, 2003 WHAT ABOUT the 3 pictures (POKEGAST, below)? As visitors to my pages may have noticed, I wear a vest with lots of pockets most of the time (I suppose this is similar to what's known as a "forager's vest"). I have a number of these vests, and if one gets wet, or muddy, I immediately change into another one. Today, August 10th, I was transferring the contents of all my pockets to a clean, dry vest. I'd spent a couple of hours smashing rice plants down with the ARGO on Creekfield Lake, and all my clothes had gotten pretty wet. As I checked my pockets one last time for small items, I found a smallish, pointy lump. I just assumed that it was a seed pod or something botanical that had fallen into my pocket during my rice argoing. When I tossed it, I watched out of curiosity as it fell. And then I noticed legs. So, I picked it back up, and put it into a small plastic vial that I had (um...yeah, in one of my pockets.) Later, at a local Starbucks (where I do a large amount of my page editing, since I use the broadband), I set up my little tripod (from another pocket) and my macro slide; and on one of their tables, I took these pictures. This is a spider commonly known by the rather ungainly name of "Crablike Spiny Orb-Weaver", and also known as Gasteracantha cancriformis. It's rather common at the park, and I thought I'd already showcased this critter on my pages, but I haven't. The web is orb-shaped, and can be identified by tiny tufts of silk on the web. These tufts look something like tiny dustballs stuck to some of the strands. I've photographed these before, but never this closely. The images below (CENTERED, and WEAVING) were taken September 01, 2002. The first picture shows some of those tufts of silk. Also, here (811kb flv video) is a clip that I took on the same day, of a Crablike Spiny Orb-Weaver weaving its orb web. If you look carefully, you'll see it touch each support strand with its spinnarets and string the cross strand.
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POKEGAST TOP POKEGAST W/ FINGER POKEGAST FRONT CENTERED IN WEB WEAVING THE ORB
I don't like moving the animals from where they live, but since this one had fallen into my pocket somehow, I already had a subject. The middle image (W/FINGER) shows the tip of my index finger with the gasteracantha. The last image (FRONT) shows it sitting in the palm of my hand. There's no telling how long the poor thing had been in my pocket. I discovered it was still alive while I was photographing it, though, so I released it outside in some garden plants, and wished it well.

October 04, 2003 About 50 miles south of Houston is the town of Lake Jackson. While I was there, I found a wilderness trail, a small park, and did a little exploring. While I was there, I found some of my arachnid friends, the Nephila Clavipes. But, as this was about 9:00 am, I was able to see the sun shining through a number of other spider webs as well, and also I found a lot of Crablike Spiny Orb Weavers; also known as Gasteracantha cancriformis.
I've shown a white one here before, and thought that I'd show that they vary in color. So, there's a yellow and a red one shown here.
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YELLOW RED SPIDER SIZE FULL WEB CENTER WEB
These spiders don't get very big (see SPIDER SIZE, above) as my index finger shows. The web is usually marked with tufts of silk, as shown in the fourth picture (FULL WEB, above) with the tufts on the edges of the web. Also note the circular center web. The other web shows the tufts near the center (CENTER WEB, above), and see how there's an open space (no cross strands) in the center, where the spider is? It was nice to enjoy the quieter pace of Lake Jackson for the day.

November 17, 2003
Now that we're looking at it, why do spiders' legs curl up like that when they die? Well, that's pretty interesting. As in the past, I went to the book Biology of Spiders, by Rainer F. Foelix, published in 1996 for an answer. Spiders' legs, as I've mentioned before, are composed of seven segments. That means that there are six articulations, or joints between them (see LEG SEGMENTS, below). For general body part names, see BODY PARTS, below. Although I used the Folix book for a reference while I made these images, any mistakes that may be apparent are surely mine.
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BODY PARTS LEG SEGMENTS HYDRAULIC PUMP
Now, most animals have two sets of opposing muscles that operate their joints. Flexors, which bend them, and extensors, which straighten them. In the spider leg, with six joints, there are two joints which do NOT have extensor muscles (from the tip of the leg, this is joint number 2, and joint number 4. see HYDRAULIC PUMP, above). That means that there are no muscles to straighten those joints! How then, can the spider straighten its legs?
While you take a moment to wonder about that, consider that spiders not only possess an exoskeleton (the "armor"), but they also have a sort of endoskeleton, or inner structural supports as well. They are called "endosterna". These serve as attachment points for certain muscle groups (entosternal muscles).
Largest of the structures of this endoskeleton is shallow cuplike construction that sort of bisects the cephalothorax (prosoma) horizontally. This is called the "endosternite". There are groups of muscles that attach this structure to the carapace (upper surface) and sternum (lower surface) of the prosoma. The picture I made above shows these in VERY simplified form. If you are interested, find the book and look at the professional version. These muscles can move the endosternite, which can lower the volume inside the cephalothorax. Doing this can increase the fluid pressure inside the spider. This is similar to you squeezing a toothpaste tube which lowers the volume, which increases the pressure, and forces the toothpaste out . This increase in fluid pressure acts like a hydraulic pump; and this is what extends the second and fourth leg joints. Without the pressure the legs will fold, if the muscles contract, and stay folded.
While this seems like an odd arrangement to me, spiders were here long before I was, so glitches in the design must have been worked out by now. Pretty complicated creatures...these "simple", "primitive" spiders.

December 18, 2003 Today's RICKUBISCAM story actually took me about 4 weeks to get the material. It started when I was looking at an orb web, and saw this string of egg sacs. Chuck DuPlant, our volunteer "spider guy", came by and showed me something interesting in the web. As the caption in the in the image below indicates, things are not what they seem.
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                                                           MORE THAN MEETS THE EYE
There's a string of eggs there, that's for sure. Here's a closer look at one end of the string (see NICE EGGS,below). Still can't see anything?(yeah...I know, it's only 320 x 240 images, but there's a lot of them.) Here, I'm pointing at the very bottom. That's my fingertip off to the left (see WEIRD EGG, below). Well, after a slight touch, one of the "egg sacs" sprouted LEGS! (see WHAT THE HECK?, below)
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      NICE EGGS!                   WEIRD EGG?              WHAT THE HECK?         I'M JUST JUNK             CYCLOSA
A little more nudging, and the "weird egg" ran off to the side of the web. It was a spider! (See I'M JUST JUNK, above). It moved off to the edge of the web, and stayed still, acting like a dead insect, perhaps. This spider, an orb weaver, is a member of the Cyclosa genus. My "Field Guide to Spiders & Scorpions of Texas", by John A. Jackman only lists Cyclosa Turbinata in Texas. There's also a Cyclosa conica (not listed in Texas that I can find), but I can't find anything to compare the two. In any case, I'm pretty sure it's a Cyclosa. The odd-shaped bumps at the end of the abdomen, and the large beadlike egg string, and the long stabilimentum also help identify this spider. Stabilimenta (plural of "stabilimentum" are the silken structures that some spiders add to their orb webs. The Cyclosa leave remnants of past meals in theirs (I've seen the name "Trashline Orbweaver" associated with this spider elsewhere.) The spider, as you can see, sits at the end of its string of egg sacs, and at the top of its stabilimentum--sort of at the junction between the two types of "web junk". The marking on the egg sacs make them look like a line of spiders:or, the spider's markings make it look like a another egg sac, while its legs twine in with the narrower tangle.
Isn't that interesting? After I disturbed it, and it ran to the edge of the web, the spider stayed still for a few minutes. Then, it quickly ran back and took its place in the center of the web. When I applied the same stimulus about 2 weeks later, the same spider didn't run, but instead simply dropped straight down, with a safety line. It hung about 2 feet below the web for a few moments, and then climbed back up its safety strand, onto the web, and back into its camouflage spot. Is that COOL or WHAT?
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          HELLO?                    RUN AWAY!                 LET ME BACK IN         CLIMBING BACK UP      I'M INVISIBLE!
In case this is hard to believe, I've got some short video clips of this spider doing its trick. The images directly above are single frames from these clips. HELLO, above, is from a clip (flv video 364kb) of it "responding" to a gentle probe. RUN AWAY, above, is from a clip (flv video 58kb) of the spider deciding to leave. LET ME BACK IN HERE, above, is from a clip (flv video 335kb) of the spider returning to hide. CLIMBING BACK UP, above, is from a clip (flv video 170kb) of the spider returning from its dropping-off ploy. And finally, I'M INVISIBLE is from a clip(flv video 327kb) of the spider moving back into place...and look how it blends! The reason that spiders do this kind of thing is still being discussed. Some believe that the spider is hiding from predators. Others believe that the spider is hiding itself from potential prey. All I know for sure is that it surprised me!

July 12, 2004 I guess it's time for a few more spider pictures. Back on June 6, I encountered a web on the Creekfield Trail with a huge beetle in it. There was also a large spider on the web, which first ran off an hid in the leaves. After just a few moments, it went back to feed on the beetle (see FROM THE VIDEO, below, or the video clip 464kb). The three images below show the beetle and the spider (see ONE'S A MEAL, below); a closeup of the spider (see GOOD EATIN', below); and a flash picture of the spider (FLASH ON THE SUBJECT, below) At the time, I was unable to identify the spider.
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                   ONE'S A MEAL                                        GOOD EATIN'!                       FLASH ON THE SUBJECT             FROM THE VIDEO CLIP
                                                                                                                                                                              VIDEO CLIP 464 kb
Then, on June 27, two of these spiders appeared at the Visitor's Center. I took a picture with a quarter, for scale, and with what is apparently the egg case (see FEMALE AND QUARTER, below). Chuck Duplant pointed out a male of the same species nearby, and so he got the quarter treatment, too. (see MALE AND QUARTER, below)      The last image is a cropped closeup of the female (see GIANT LICHEN ORBWEAVER, below). Many people were calling this a "Marbled Orbweaver" and that's probably a reasonable identification for this spider. However....
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            FEMALE AND QUARTER                           MALE AND QUARTER                      GIANT LICHEN ORBWEAVER

I was looking through my Field Guide to Spiders and Scorpions of Texas by John A. Jackman, and there, in the color plates-on P 8, no. 21c at the bottom of the page- is a spider that is very close in color and shape to this one. Without going into anatomical detail, it is very difficult to be sure of the species and genus of many spiders. But, I looked at the latin name for this spider in the book, Araneus bicentarius; and looked through the few books I have. I couldn't get a good cross reference, though. However, I looked on the internet, and found a few good matches, with pictures that look very similar to mine (I find the white Rorschach pattern at the front of the abdomen quite striking). With some of these pictures was listed the common name "Giant Lichen Orbweaver". I think this is a very descriptive name, considering the size and greenish (resembling lichen) color of the back of the spider. So, that's the identification I will use for this spider.

If you'd like to know more about the park follow these links:

Brazos Bend State Park The main page.

Brazos Bend State Park Volunteer's Page The volunteer's main page.

Click on this image to see a flv video movie (942kb) of a series of 9 11 x 14 posters I'm working on.

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