Learning to Love the Cross Orbweaver Spider

Our unavoidable arachnid neighbors are worth a second look

Posted November 21, 2011 by Katy Evans

Every year, as fall descends in chill and darkness upon us all, an inevitable harbinger creeps out, silently proclaiming the season by bedecking gardens, scuttling through leaf piles, and dangling directly in our faces.

As commonplace in Northwest fall as clouds, the Cross Orbweaver (Araneus diadematus)–also known as the European Garden Spider, Diadem Spider, or Cross Spider–takes up residence for the season,  their pervasive webs stringing across windows, from tree to tree, from dahlia to chrysanthemum.

Not sure which spiders I mean? Cross Orbweavers are identified by the distinctive pattern across their backs, usually formed by five or more large white dots joining to form a cross. Individually the coloring of these spiders can range from  a mottled dark grey, brown and orange to light yellow but all bear the characteristic cross.

Adult females range in length from a half inch to just over an inch, and the males are much smaller, generally half the size of females.

But what are these guys really about? Is there more to this web spinner than meets the eye?

When it comes to animals, I am of the opinion that there’s always something fascinating to uncover, no matter how common the species. And although the Cross Orbweaver is possibly one of the most common spiders in North America (known from Pennsylvania north through New England, across Canada, and south into Washington, Oregon, and California) there is of course more than can be deciphered at first glance. Like that fact that is not a native species to North America and came here by way of Western Europe!

I’m not a spider fan, just generally curious, so although I was very interested to learn, it took a significant amount of will to power through internet research with results like this and this. Who, besides actual arachnologists, actively seeks out this kind of intimacy with spiders? Way more shudder-inducing familiarity than I require.

That said, I’ll share a calming, appreciation-inducing fact: pleasantly, the Cross Orbweaver prefers the out-of-doors so usually its presence is reserved only for occasional outside surprises.And, of the two broad categories entomologists have for spiders, our new friend the Cross Orbweaver is considered a trapper spider, a much more passive predator than ambusher spiders.

Calming Nerves, Dispelling Myths

For those still feeling skittish, let’s dispel some fears and myths: spiders are not a threatening or even regularly deadly species. Although most spiders have a low level of venomous potential, they rarely bite and people rarely suffer desperately from bites.

In fact, according to the Burke Museum,

“There is no spider species anywhere that can properly be called ‘deadly’…I know of no species anywhere on earth capable of causing death in humans in as much as 10% of cases, even if untreated. If the person bitten obtains medical aid, death from genuine spider bite is almost unknown in North America and a decided rarity worldwide.”

Spiders are shy hunters and rarely attack anything larger than themselves. Now that’s out of the way – let’s move on and develop enthusiasm for the artistry of their web-making ability!

Spin for Your Food

Cross Orbweavers are tremendous web spinners, and, as their name suggests, are part of the spider family responsible for our classic spiral ideal of a spider’s web. Not only are these spinners artistic, they’re also discerning about placement: who knows how the knowledge evolved, but it is common to see Cross Orbweaver webs under porch and street lights, and other areas known to attract insects. And by Cross Orbweavers, I really mean the lady Cross Orbweavers. Although the male Cross Orbweavers are spinners too, their webs are significantly smaller (and, let’s face it, less spectacular) than the females’ webs.

Once the web is complete, the Cross Orbweaver can be found hanging out in the direct center, head down, ready to skitter quickly to stun and wrap any prey that may bumble its way into the web.

Also, unlike messy web spinners like cobweb and cellar spiders the Cross Orbweaver is fastidiously and industriously tidy: typically each night these spiders dismantle and eat their web, take a short break, then rebuild a neat, clean new one all ready for collecting breakfast.

The very act of web spinning by a Cross Orbweaver is a captivating feat of instinctual engineering. She begins by floating a line on the wind to a nearby surface. She secures the line and then drops another from the center, making a “Y”. The rest of the scaffolding follows, all constructed with the spider’s nonsticky silk. Once the radii are in place, the spider can move from strand to strand, attaching the spiral of sticky capture silk.

Web-building requires some special equipment — web spinners craft webs using three claws, two to place silk and one to navigate the spider on the nonsticky threads. Spider silk, a very strong and resilient spun protein fiber, is not simply for web building and capturing prey; Spiders also rely on silk as climbing rope to travel and to aid in quick escapes.

Gaining Perspective

In order to really grasp the significance and importance of spiders, I recommend a prehistoric perspective: fossil evidence shows that orb weavers have been around a very, very long time. Three of the major orb weaving families (Araneidae, Tetragnathidae and Uloboridae) were in existence 140 million years ago and most likely originated during the Jurassic period.

And from the historic to the historically scientific: it turns out that insects and spiders have become more diverse and varied at comparable rates, suggesting that, near simultaneously, new species of both developed and spread out into new habitats. Fascinatingly, the peak of this expansion and diversity occurred before the origin of angiosperms (flowering plants).

Two scientists, Fritz Vollrath of Oxford University and Paul Selden of the University of Kansas made the bold proposition that insect evolution was driven less by flowering plants than by the predatory behavior of spiders.

They stated in 2007: “Spiders’ silks and webs have made it possible for this diverse taxon [a group of organisms] to occupy a unique niche as the main predator for another, even more diverse taxon, the insects. Indeed, it might well be that the spiders, which are older, were a major force driving the insects into their diversity in a coevolutionary arms race.”

Spiders are found the world over on every continent except Antarctica and can live successfully in every land-based habitat (no sea or airborne spiders yet!). Estimates on spider population range widely but there can be up to 5 million spiders per 2.5 acres.

Spiders rank seventh in total species diversity among all other groups of organism, and as of 2008, approximately 40,000 different spider species have been identified. By comparison, there are only 4,000 identified species of mammals.

Now that we’ve explored their looks, habits, talents, and historical relevance, I think we can only conclude with the significant benefit provided to us by these eight-legged friends: spiders are one of nature’s most advanced and effective predatory insecticides. As P. Allister say in this article from Fountain Magazine:

“It is high time human beings overcame their irrational detestation of spiders. We should be grateful to them for all the good they do for us in preserving our persons and properties, especially our crops, against devastation by insects. One authority calculated the spider population of England and Wales as of the order of 2.5 billions at any one time. This means that if (at a most conservative estimate) each spider eats 100 insects a year, then the total number of insects consumed by spiders is 250 billions annually.”

That is A LOT of insects that, thanks to spiders, won’t be bothering, biting, and spreading disease, and that’s just in England and Wales. It is estimated that the weight of insects eaten by spiders every year is greater than the total weight of the entire human population.

I know I don’t need Cross Orbweavers to do anything more than they already do for us. They eat bugs, sport fascinating fancy patterns on their bulbous little bodies, make aesthetically satisfying webs and generally keep out of the way. How can you ask for more in an unassuming, quiet, diminutive, only occasionally startling animal? Hopefully you will now all consider joining me in giving a slight appreciatory nod to our spinnerly neighbors, the Cross Orbweavers, the next time you pass one by.

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