Spider Silk Miscellany

During my searches about argiope trifasciata (banded garden) spiders for "Argiope Trifasciata Spider--Final Bug Spotting of 2017" and "Argiope Trifasciata Spider--Doggone Buggone at 2018 Start", I collected information about spider silk, webs, stabilimenta, and Charlotte's web. IMHO, the most interesting information about spider silk is specialization. Spiders produce different silk for different purposes, coming from different "extruders" called spinnerets.

Spider Silk and Webs
From "How Do Spiders Make Silk?"

The silk that spiders produce is five to six times stronger than high-grade steel by weight, and is stronger than any known natural or synthetic fiber on Earth.

From "Smooth as Silk"

All spiders produce silk but not all spiders spin webs. Silk is used for climbing, to create webs, to build smooth walls in burrows, build egg sacs, and wrap prey. … Most spiders have four or more openings, or glands, on their abdomen called spinnerets. When the spider releases the silk, it looks like one thread but it is actually many thin threads that stick together. ... Larger spiders, like the huge bird eating spiders, can actually catch and subdue animals as large as bats, mice, fish, birds and even snakes with their strong webs.

From "Spider Webs"

Web-Spinning Spiders … know when prey is trapped on their web by detecting and reacting to the vibrations the line makes from their prey moving and trying to get free.

Spiders have seven pairs of silk spinning organs or glands called “spinnerets” located either in the middle or at the end of their abdomen. Each spinneret on the spider is different from the other and used for making several kinds of silk: …

Web-Spinning spiders only use the tips of their legs when creating their webs so that their body doesn’t come in contact with the web and get stuck.

From "8 Silkily Engineered Facts About Spider Webs"

The basic structure includes radial threads that extend out like wheel spokes from the center. Another set of threads spiral out in concentric circles. The silk used to construct these two parts of the web is actually produced by different glands, which is why one is sticky and the other isn’t.

From "9 Amazing Facts about Spider Silk"

while the spider is not the only animal that can produce silk, it is the only animal that can produce different types of silk for different purposes. They can produce fine threads (called gossamer) and thicker threads, as well as both sticky and non-sticky threads.

From "Spiderweb vs. Cobweb - What You Need to know"

COMPLETE SHOW NOTES for this episode found at http://askahousecleaner.com/spider-web-vs-cobweb/.

Charlotte's Web
From "Charlotte's Web - WHO IS CHARLOTTE?"

Charlotte is a "barn spider." Her scientific name (today) is Araneus cavaticus. Her ability to spin orb webs is one of Charlotte’s characteristics.

From "10 Things You Might Not Know About Charlotte’s Web"

E.B. White created beloved characters out of the most unlikely of animals—a runt of a pig named Wilbur and a spider named Charlotte, who weaves words in her web to save his life.

From "Why Spiders Decorate Their Webs"

White wrote Charlotte's Web after marveling at the intricate patterns in a spider's web in the barn on his Maine farm. While we've yet to discover a real spider capable of weaving "some pig" or "terrific" in silk, we do know of many spiders that decorate their webs with zigzags, circles, and other fancy shapes and patterns.

These elaborate web decorations are known as stabilimenta. A stabilimentum (singular) may be a single zigzag line, a combination of lines, or even a spiral whorl in the web's center. A number of spiders weave stabilimenta into their webs, most notably orb weavers in the genus Argiope. Long-jawed spiders, golden silk orb weavers, and cribellate orb weavers also make web decorations.

More About Stabilimentum
"stabilimentum, stabilimenta"

In the Identification section of "stabilimentum, stabilimenta" Info tab—"conspicuous structures of heavy silk found in the webs of some orb-weavers (Araneidae)."

Recent Spider News Odds and Ends
From "Spider drinks graphene, spins web that can hold the weight of a human"

The webbing was on par with bulletproof Kevlar in strength.

From "How One of the Fastest Spinning Animals Catches Its Prey"

Flattie spiders can strike at speeds up to 3,000 degrees per second. That means that in the time it takes you to blink your eyes once, they can complete three full rotations.

From "Part spider, part scorpion creature captured in amber"

two independent teams describe four 100-million-year-old specimens encased in amber that look like a cross between a spider and a scorpion.

From "Eighteen new 'pelican' spiders discovered in Madagascan rainforest"

Pelican spiders were first discovered in the mid-1800’s, embedded in a piece of amber from the Baltics.

An ordinary house spider’s body is divided in two parts: the abdomen behind and cephalothorax in front, where the eyes sit above the mouth … But a pelican spider has an elongated head with eyes on top, and a long neck like a giraffe. The mouth sits at the base of the long neck …

Argiope Trifasciata Spider--Doggone Buggone at 2018 Start

Tch! On the last day of 2017, I took pix and video of an argiope trifasciata spider. (For background, read "Argiope Trifasciata Spider--Final Bug Spotting of 2017".) The next morning, I went to the web; she was nowhere to be found. Over the next few days, we’d peered into the plant—no sign of the spider, nor indicators of web disturbances, nor egg sac.

I’m guessing that the spider did not undergo a "normal" life cycle. From BugwoodWiki's “Banded Garden Spider”:

The overwintering stage is the eggs, which are protected within an egg sac attached to vegetation. Upon hatch in spring the spiderlings disperse, … Adult males begin to appear in late July and females shortly afterwards. The males wander while the females remain within a web. Mating occurs in the latter half of the summer and females produce egg sacs, … Freezing temperatures kill off all remaining spiders at the end of the season and they have a one year life cycle.

I’m going out on a limb here. The case for the spider to not having been there in the summer and fall is lack of any egg sac since having spotted her on New Year’s Eve. I propose that the weather, fast approaching freezing, resulted in lack of prey or male, possibly (probably?) influencing her to abandon her web.

I gleaned the following temperature info from December 30 through January 3 results, using Weatherunderground's Wundermap for my area:

December 30 temps—high in low 60s at noon, temp 49ish around 8 PM when we spotted the spider.
December 31 temps—40 at AM start, 37ish around 8 AM when I took pix of the spider, gradual temp drops.
January 1 temps—mid-20s at AM start, less than 30 throughout the entire day and evening.
January 2 temps—lower than 30 throughout the entire day and evening.
January 3 temps—20s at AM start, climbing to 30s around 9 AM, climbing near 60s around 4 PM, then cooling down as evening progresses.

I speculate that the spider constructed the web during reasonable temperature, before the freezing temperature set in and that lasted a few days. During the freeze, prey maybe didn't approach the web (unwittingly or not); thus, no food for the spider. No male argiope trifasciata spider approached the web for mating; thus, no need for the female to create an egg sac.

A few successive days of looking at the plant and noting the intact web, I sensed the female abandoned the web. I ruled out the possibility of a predator making a meal of the spider. I think a struggle would have resulted in the web being wrecked.

One other oddity: The orb web did not have a stabilimentum (elaborate web decoration) as I've noticed in several other images of female argiope trifasciata spider webs. The lack of stabilimentum might have indicated the stoppage or interruption of the spider's "housekeeping setup" process. Read more about stabilimenta.

Curious about doing your own weather timeframe lookup? Start at https://www.wunderground.com/wundermap.

1. Confirm or click All Layers > Weather Stations > Temperature / Wind.
2. At the search field, enter your city of interest, then enlarge the view to the scale you want.
3. Scroll to the area of interest. (The results might be slow to arrive.)
4. Click a number. When the inset window opens, click Visit local weather page for [your locale].
5. At the new window, scroll down to the weather history options. The first option is interval, the default being daily. You can set for larger intervals or customize for date range. View graph or table.
6. The newer window has an enlargeable inset map with additional station numbers you can click and find similar information.