“A Fly that had been crawling along Wilbur’s trough had flown up and blundered into the lower part of Charlotte’s Web and was tangled in the sticky threads. The fly was beating its wings furiously, trying to break loose and free itself.

“First,” said Charlotte, “I dive at him.” She plunged headfirst toward the fly. As she dropped, a tiny silken thread unwound from her rear end.

“Next, I wrap him up.” She grabbed the fly, threw a few jets of silk around it and rolled it over and over, wrapping it so that it couldn’t move. Wilbur watched in horror. He could hardly believe what he was seeing, and although he detested flies, he was sorry for this one.

“There,” said Charlotte. “Now I knock him out, so he’ll be more comfortable.” She bit the fly. “He can’t feel a thing now,” she remarked. “He’ll make a perfect breakfast for me.”

                “You mean you eat flies?” gasped Wilbur.

“Certainly. Flies, bugs, grasshoppers, choice beetles, moths, butterflies, tasty cockroaches, gnats, midges, daddy longlegs, centipedes, mosquitoes, crickets—anything that is careless enough to get caught in my web. I have to live, don’t I?”

“Why, yes, of course,” said Wilbur. “Do they taste good?”

“Delicious. Of course, I don’t really eat them. I drink them—drink their blood.”(White 1952).

 Figure 5: Argiope aurantia with lunch. Photo by Todd A. Blackledge 1997

So males have it rough, but it’s tough being a lady spider too: she’s kind of intimidating, she’s got to destroy and rebuild her home every night, she eats and essentially kills her lover and then she never gets to see any of her 1,400 children. She builds these fantastic papery brown egg sacs (usually no more than three—see figure 6) and watches over them until the first frost, when she dies because she can’t stand the cold. When her babes emerge in the spring, they drift away in the first wind. There’s nothing of her left. She’s got no bones to fossilize and her web probably went to pieces in the first winter storm.

Figure 6: Argiope aurantia with egg sack. Photo by Emile Zeringue, courtesy of Mark Moran 2002.

Figure 7: Spider Timeline (Amonline 2002)

The following part continues from ENTELEGYNAE:

And this is why tracing spiders’ evolutionary path has not been easy. Although spiders were some of the earliest animals to live on land, their fossils are hard to come by. We can surmise that they evolved about 400 million years ago; the first definite spiders—thin waisted arachnids with abdominal segmentation and silk producing spinnerets—lived 380 million years ago in the Devonian Period, more than 150 million years before the dinosaurs (Amonline 2002).

The earliest spider fossils are of Attercopus fimbriungus; these spiders lived over 380 million years ago and like other primitive spiders, their spinnerets were in the middle of their abdomen. Most early spider fossils belong to a group of spiders called the Mesothelae, whose spinnerets were also in the middle of their abdomen. They probably lived on the ground, only using silk to protect their eggs, to line a retreat hole and later perhaps to construct ‘trap doors’(Amonline 2002). However as plant and insect life evolved so did the spider’s use for silk (Ramel 2003). More than 250 million years ago, spiders with spinnerets at the end of their abdomen appeared (see figure 7). It’s likely that this anatomical change enabled the development of more elaborate webs to capture prey both on the ground and in the foliage.

By the time dinosaurs were roaming the earth, the complicated aerial webs of the orb-weaving spiders were ensnarling increasingly varied multitudes of flying insects. Likewise, more and different types of hunting spiders in the litter, bark and foliage progressed as a result of new prey-capture and habitat options (Amonline 2002).

Although all spiders have silk glands, some spiders weave webs while others do not. In fact  “all spiders have at least three kinds of silk glands and most species have five,” but many species of spider don’t use those glands to weave webs (Spider Pages 2003). Inasmuch spider’s have been divided into two camps: Cribellate and ecribellate. Orb weavers are cribellate, meaning they have a special organ, called cribellum, which helps them spin their webs. Tarantulas are ecribellate. Ecribellate spiders evolved from cribellate spiders (Shear 1986). Web weavers were the first spiders, though that doesn’t make web-weaving spiders more ‘primitive’ (in many ways ecribellate spiders appear more ‘primitive’ because of their large size, their less flexible chelicerae and so on) just older in evolutionary time.

Because ecribellate spiders, such as tarantulas, do not weave webs, they have evolved with a larger size, at times, more paralyzing poison and larger “fangs.” Their habitat, their prey capturing techniques, reproductive habits and so on all reflect and are a consequence of their evolution. Likewise, web-weaving spiders weave different kinds of webs and these various web types reflect different evolutionary paths. Orb webs, dome webs and sheet webs are just a few examples of different web types. Interestingly enough, one of the most complex of these webs—the Orb web—is the ‘mother web’ as it were, or the origin of all other web types. Many scientists believe that orb weavers, like Argiope aurantia, and their orb webs were some of the earliest examples of spider life and habit. They are the foundation upon which more ‘primitive’ forms of spider webbing evolved. However this theory is hard to prove because it can’t be demonstrated in the fossil record and so some entomologists do not accept it (Ramel 2003).

Aside from spinning many different varieties of orb webs, orb weavers have just as varied prey capturing techniques. These techniques are also used to distinguish different evolutionary paths. While the orb-weaving genus Nephilia captures prey by delivering a quick bite and then eats, orb weavers in the genus Argiope (like Argiope aurantia) bite, then wrap, then eat their prey later. Although, Argiope’s technique varies depending on her mood: sometimes they wrap the prey in silk before biting it. Some spiders, such as Tetregnathids, “rotate their prey with their hind legs while wrapping them…allowing them to deal with (the prey) much more quickly.” One way to understand the difference in prey-capturing techniques is to look at where these spiders weaves their webs. Nephilia weave webs in physically higher locations than Argiope. Nephilia tends to catch flies and smaller insects, where as Argiope tends to catch grasshoppers and larger insects. Argiope wraps prey before eating as a security measure: bite now, wrap now and eat later, when this comparably large insect is less dangerous, i.e. once the poison has totally subdued the prey (Ramel 2003).

There are as many behavior types as there are spiders. Different species of spiders attest to the tremendous complexity of life; they demonstrate how perfect an organism’s niche can be despite the awesome array of options. There are perhaps over 40, 000 different species of spiders (Nieuwenhuys 1999). They are some of the oldest forms of life on the planet and perhaps are even more ancient than we think: Lack of evidence doesn’t mean they didn’t exist before the Devonian, a mere 400 million years ago. Modern man only appeared 60,000 years ago and for most of that time, our ancestors struggled to master what spiders had accomplished eons ago: having a home, getting food, ensuring their children’s survival, etc. Spiders are an r-selected species; there is no parental investment and yet baby spiders know how their species weaves webs, how they capture prey, how they mate, what they eat and so on. Individual spiders are genetically programmed to weave a very specific kind of web and they do so without fail. This is a truly incredible evolutionary feat.

 Figure 8: Cladogram of Araneidae. (Tree of life 2001)