Photo Adventures with Curiosity and Learning


Name: Masha
Species: Jewel, Crab or Spiny Spider Gasteracantha cancriformis or Gasteracantha elipsoides
Kingdom: Animalia
Phylum: Arthropoda
Class: Arachnida
Order: Araneae
Family: Araneidae
Genus: Gasteracantha
Species: Gasteracantha cancriformis
Range: North Carolina to Florida and west to California
Color: Black with yellow dots on the bottom. White with black dots on the top. The spines are red. The length for the female is about 15mm
Eating habits: Small flying insects but otherwise, unknown by me
Reference:

Featured Creatures, Univ of Florida,

Texas A and M

Spider Photos

Masha, a new resident, appeared in our neighbors front garden with a web that was about 45 degrees (i.e. not vertical). It was quite loose in that a slight breeze would move the web 5 - 10 cm. There are lengths of thick silk dispersed along the supporting threads, though I've not been able to capture this with a photo.

This spiny or jewel spider (some call her a crab spider) ( Gasteracantha cancriformis or Gasteracantha elipsoides ) has very interesting coloration. White with black dots on the top and then black with yellow dots on the bottom. The spines or horns are short, a few mm, and reddish-orange in color. In low light its difficult to see the colors, but captured on a photograph, they are truely beautiful.

This afternoon I was able to catch a web building exercise. As I was walking home, I noticed that there was only a skeleton framework of the web. Then I located Masha, she was weaving the radial segments. She extruded silk to build 2 segments in on direction and then 2 segments is approximately 120 degrees and then another 2 segments rotated another 120 degrees. Why 2 segments? She places one segment from the center to the perimeter, attaches it, then moves about 3-4 cm away and using the previous radial spoke to move back to the central core where she attaches the 2nd spoke. She then selects another direction, makes an outward directed spoke, moves 3-4 cm along the perimeters and then makes an inward directed spoke.

After finishing all the spokes, she weaves the circumferential fibers as one continuous spiral link. Unlike the banana spider (Nephila clavipes), the spiny (Gasteracantha cancriformis) makes one weave of the circumferential elements, not a course weave and then filling in the gaps. I have some video that I shall try to extract segments to demonstrate the weaving. It is very fast, and with even a slight breeze, the web is moving such that focus is difficult.

Early Morning Photos - a bit fuzzy because of the motion of the web in the morning breeze

The spiny, crab or jewel spider ( Gasteracantha cancriformis ) has turned out to be a very interesting spider. She looks like a small crab with 6 red spikes. She is quite small (about 1 cm) and she is either weaving or simply hanging around, I guess, waiting for something interesting to happen. The web, angled at about 45 degrees, seems not very optimal for catching small insects, and is readily distorted with gentle breezes. Almost impossible to take a well focused photo due to the continuous motion of the web. The web is also interesting in that there are 3-4 cm lenghts of heavy silk, spaced in a pattern - so that you see a full web with these regions of thick white silk - perhaps as a signal for larger flying food to avoid the web, as it would surely be destroyed. (click each image for the full presentation):

Note the distortion of the web due to the Masha's weight. Not a very tight weave. A spiny spider does not weave a tight web and so her weight as she weaves, makes very interesting patterns. See the pattern of the circumferential segments?
Another presentation of the web and her weaving. Here I think she is reinforcing a radial fiber.

Her web

Playing the web like a harp

Spinning - note the silk being extruded from her spinneret

Another view of her spinneret

Her body as a silhouette

Her spines (6, but one is hidden)

Making music on her harp

I'm not sure what she is doing here

Afternoon photos

This illustrates the size scale - a 1 cm spider with a 1 meter web Click on the image to see the full presentation.

Weaving again - better focus

A web in disrepair. I suspect in the morning, she will weave new segments

Illustrating the web with a low intensity flash (finger covered half the flash)

Highlighting the horns with a low intensity flash

Various Aspects of Building a Web

The spiny or jewel spider ( Gasteracantha cancriformis ) builds her web within a super structure of fibers that form a rough pentagon as seen below. The super structure threads have periodic segments of thick silk, I suppose to warn birds etc - that there is an obstacle within. Her web consists of spokes from the periphery convergion on a central hub and a circumferential element, woven like a spiral.

Video Segments (15 sec and 1 min) of weaving circumferential segments Apologies! The motion is due to web movement associated with a slight breeze. Also - the mp4 video may not render with all players - use mov with quicktime if there is a problem. The mpg files should render fine on any player.

(click each of the below images for the super-size):

Superstructure and web - note the thick white silk segments that outline the pentagonal outline of the superstructure. The superstructure is outlined in red while the yellow ellipse contains the majority of the web. Masha is located near the center of the elliptical region.
Inner web structure of the web. The circumferential element is placed as a spiral - starting from the outside and then gradually moving closer and closer to the center.

The thick white segments on some of the radial segments appear to be a signal to large flying things - to avoid the web, thus protecting it so that smaller insects who do not notice the markers will collide with the web, creating a tasty treat for dinner
Here is shown the core of the web with a coarse spiral from the center out to the circumferential components.
Extrusion of silk - note the silk being extruded from her spinneret
A slightly different view of extruding silk from her spinneret
I believe that here, she is attaching a radial segment to the central hub
Here, I believe she is organizing the attachments of some radial segments to the central core.
A different view of organizing the attachment of radial segments to the central core.
Extruding and attaching a radial segment to the central hub
Extruding a radial segment
Extruding and placing a radial segment. She is dropping down, by gravity to the superstructure, where she will attach this segment - then walk about 3-5 cm along the superstructure and then while climbing back to the central hub, she will be extruding another radial segment for attachment to the central hub.
Looking at the web edge-on
The completed web - superstructure, spiral core circumferential weave.

Creative Commons License
This work is licensed under a Creative Commons License.

C. Frank Starmer

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