Crab Spiders

Oregon: July 2011

We have a date with a halibut -- we hope. In recent years commercial halibut season off the Oregon Coast has been carefully restricted to ensure a continued harvest. This year there was a ten hour season in late June. We placed an order for a 15 pound fish. Unfortunately our fisherman didn’t catch enough and we didn’t get our fish.

Yesterday was the second and last one day season for halibut. We don’t know if we got a halibut, but we’ve come over to the coast hoping. We have plans to pick 80 plus pounds of blueberries tomorrow, so picking up the fish tomorrow isn’t an option. Even if we don’t get a fish today, a trip to the Oregon Coast is always welcome.

First stop is a little picnic site in the Oregon Dunes Recreational Area. We have got the area to ourselves. So peaceful. Sun is just beginning to win over clouds. The bushes next to me are laden with big droplets of water. A bowed grass stem has droplets every half inch. I’ve got the lazies. I fall asleep with the car window wide open.

Zoom! A humming bird rudely interrupts my cat nap. The hummer is attracted to my red shirt and came within inches for an inspection. Ah well. I should be poking around to see what I can see.

We’ve parked next to a mowed clearing about the size of half a city block. A creek runs along he northern edge and the rest is surrounded by dense bushes easing into dense forest. The Oregon coast gets plenty of moisture and becomes almost impenetrable along its edges.

Pretty quiet. I hear varied thrushes, crows and wrentits, but can’t see any birds to sketch. An eight-spotted dragonfly lands near me. They like to ‘hawk’ for prey from an exposed perch. He sits and waits, then zips out and back to a different perch. Luckily I sketch quickly. He soon flies off, heading upstream.

The nearby blackberry bush is buzzing with bumble bees. One sits still for me and I start to sketch, expecting him to take off at any moment. (It’s the little black and white sketch on the left)

Duhhhh! I’m nearly done with the black and white sketch when I realize this little bee isn’t going anywhere. The bee hangs in the clutches of a big, white crab spider. The spider blends so well with the blackberry blossom that I didn’t notice until now!

The bee hangs motionless. The spider’s jaws are sunk into the bee’s forehead. Even with this going on other bees come and go, landing on the same blossom. Beneath the crab spider lies another bee, I assume an earlier victim.

Spiders inject a deliquescing solution, then sip out the spider’s innards. It is a slow process, so I have time to sketch.

After we are home I read a little about crab spiders. They are ambush predators, i.e. they wait for prey to come along and grab. Sometimes they wait in the same spot for days, even weeks. No stringing a spider web needed. Some crab spiders can gradually change color to match their surroundings. I soon find there are over 200 species of crab spiders just in North America, so there is little chance I’ll figure out exactly which spider I found, but I do know from the fat abdomen that it is female. The males are much slimmer.

Three days later I find two dead insects resting on a blackberryleaf. I remember my recent encounter and look higher in the bush. Sure enough! There sits a crab spider, sipping on a bee. This spider is a purer white and has faint pink markings on the sides of her abdomen. Already the bee appears to have had most of its juices sucked out. It is looking pretty ratty. The spider sucks on the abdomen for another half an hour, then drops it off her leaf.

Once finished with dinner, the crab spider immediately goes into her hunting pose. She sits on a leaf with with two legs spread open ….. waiting. We wait too. Wouldn’t it be exciting to see her actually grab a fly or bee! One comes near, but she is a patient lady, and waits for exactly the correct position. The bee flies off, not knowing what a close encounter it just had.

Careful inspection of the spider shows that her two front legs are much longer than the two back legs, thus giving her the ‘crab’ appearance. She uses the front ones for grabbing prey while she anchors herself with the back legs.

We wait with the spider for half an hour. She sits near enough to a blossom to reach out and grab should a bee land on the near edge of the flower. One bumble bee almost gets into position. The spider reaches out to touch, but the reach seems too far.

Gradually we lose our light and raindrops start to fall. Just as we are thinking about leaving we see her slip underneath the leaf and out of the rain. All I see now are the tips of her legs on one side of her body. The bees have quit flying and darkness will take over before long.

Time to head home.

* * *
Two days later: “Along came a spider and sat down beside her” …. This old nursery rhyme has been running through my head. I guess I’ve still got spiders on the brain. Now that I’ve found a couple of crab spiders I seem to keep bumping into them.

Two days after finding spider #2, Dale photographed a Washington lily growing in the Umpqua National Forest. When we got home, much to our surprise, we spotted another white and pink crab spider tucked deep in the blossom. Just a couple days later we were back at the same spot. Ms. Spider was still tucked in the same blossom and feasting on a large fly.

Suddenly crab spiders seemed to be everywhere. I found a bright yellow one feasting on a robber fly who got too near the daisy she was perched on.

Later in the day I sat down next to a crab spider so I could do a careful field sketch. She was beautiful -- bight yellow and strong red markings. She quickly accepted my presence even though I was only three feet from her. I nearly finished this little sketch before the flies and the heat drove me into the shade. I had watched for a good half hour without her catching any prey.