Traplines in the air

It's going to be a good summer for watching spiders. The rhododendrons and cedars on the sunny side of our lawn are festooned already with big webs. The spiders, female Araneus diadematus, aka cross spiders, are still tiny, barely an orange speck in the centre of each web. They'll grow; by the end of the summer some will be up to an inch across, fat bellies showing their success as trappers.

They hang, belly out, upside-down, in the centre of the web. One back leg holds a drag line attached outside the web. This spider has caught and wrapped some sort of fly. An early supper!

"It is common for a web to be about 20 times the size of the spider building it." Wikipedia

Another spider, still waiting for her prey.

These are seriously smart critters. Building a web isn't just a rote operation; every site has its special requirements, and the webs are more elaborate than the simple spiral and ray arrangement shown in children's books.

The spider launches a thread from the top of her chosen location, waits until it makes contact with another branch, then runs down it to glue it down well and reinforce it. She picks a centre and builds another ray out from there, then more until she's filled her space. Then she makes a small spiral in the centre, using non-adhesive silk, glued together where they cross the radials. This is her resting place and launch pad.

8 rounds in this spiral. Note the glue spots at the nodes only.

Then there's a gap, about twice the diameter of the inner spiral. What is function is, I don't know. Maybe it keeps the struggles of her prey out of her private space. Only she really knows.

Then comes the business part of the web. She fills most of the available space with more spirals, built first with non-adhesive silk, then replaced with the sticky stuff. (She eats the first lines; spiders recycle!) She leaves more dots of glue here, spaced randomly, not usually on the nodes.

Outer web. Note the glue spots. The rays are not sticky; the rest is.

And here's where her web differs from the standard drawing; every so often, along those regularly-spaced spirals, she breaks the pattern to make an X, sometimes a Y, sometimes a knot of angled threads. The spider at the top here has a large area like this near the inner edge of her trap; the second spider is a bit more restrained, sticking to a few simple Xs and offset sections.

I was inclined to think of these, at first, as mistakes, the spider losing her way briefly, getting confused. But every cross spider does this; it probably has some function. Maybe it's like the trusses in bridges and roofs, using the triangular shape to add more strength.

What went on in the spider's head? (Or belly, or legs, since her brain is too big to fit in that little cephalothorax, and she's outsourced it to several parts of her body, including the legs. Up to 80% of that little body is brain.) How does she decide it's time to change direction? Does she do the math? Or just sense some instability in the web and X it out?

Questions, questions.

As I sit here typing, a pinhead spider has been busy building a web on a sparrow feather beside my desk. She came down the wall, jumped the gap, and made a beeline for that feather, climbed it and dropped her anchor. How did she know the feather was there? How does she figure that's a good hunting spot?

And what will she be catching. She's so small I barely see her; does she see my desk crawling with little beasties that I can't see? Now I'm itchy!

Sunshine Coast trip, Day One

Delta to Trout Lake:

(I'm going to try to blog our wanderings in chronological order. More or less.)

We left home in Delta as soon as the morning rush hour was over, and in spite of construction hold-ups and the post-rush-rush, had time for a walk and coffee in Horseshoe Bay before our ferry arrived. The weather was perfect; sunny and warm, with a few wispy clouds here and there, and enough breeze off the water to keep us comfortable.

View from Horseshoe Bay. Marina and ferry (not ours)

Lunch on the ferry. The windows were so grimy and splotched that it was discouraging to try to watch the scenery for long. We took out books and read instead. I think that's the first time I ever did that on a ferry. (For shame, BC Ferries Corp.!) For once I was glad that the trip only takes 40 minutes.

We stopped in Roberts Creek to visit a potter's studio. (Oops! Here's my first deviation from strict chronology; we still haven't unpacked the box of goodies we bought there. More on this later. The best laid plans ... )

Next stop, Trout Lake.

Step out of the car, point, and shoot. Laurie says you can't go wrong on the Sunshine Coast.

This little duck was swimming alone, ducking into shore among the shadows. I found it hard to identify birds on this trip; the adults are molting, the youngsters are half-dressed.

A bee was poking around in the face of the rock, as if it were a flower. I don't know what he was finding there.

We followed a path across a low hill to the other end of the lake, to see the water lilies. The soil on the hill is dry between the rocks, and covered with brown evergreen needles and cones. Salal, huckleberry, and hardhack cover the sides. 

Hundreds of these spiders make their very messy webs on the salal plants.

As near as I could get to one without breaking into the web. Unidentified spider, so far.

Back to the car, and on we went. We had another ferry to catch.

To be continued ...