Carl the Crab Spider (Coriarachne brunneipes)
My mother used to read a book to me when I was a small child called Be Nice To Spiders! The little boy in the book brings a spider (named Helen) to the zoo in a matchbox because he isn’t allowed to keep her in his apartment. When the zookeeper opens the box, Helen escapes and sets up residence in the animal cages where she helps all the animals by eating the flies that make them miserable.
This story was one of many experiences I enjoyed that set me up for a lifetime of observing invertebrates and their behaviors. Today, I am sharing about a small crab spider I found in our house this week. It took me all week to identify it, but I persisted and even managed to keep the little guy safe from Millhouse. Millhouse is the resident cat. He likes to eat spiders. That’s another story and a good one, but I’ll save it for next time.
Today, meet “Carl” the Black Crab spider, also known more formally as Coriarachne brunneipes. Black Crab Spiders are classified taxonomically in the family Thomisidae (Crab Spiders), genus Coriarachne, and species brunneipes. They are found ranging across the Western U.S. from the Rocky Mountains to the Pacific Coast…and in my case, on San Juan Island, WA. 98250! The Black Crab spider is relatively small in size. About 1.9 cm or equivalent to the diameter of a penny if you include its leg span (see photo below from Wednesday, April 25, 2018).
You can also see in my photo that Carl is missing a leg! 3 + 4 only equals 7 and spiders have 8 legs! Maybe Millhouse DID do something to this spider after all!
I left Carl to go about things on Wednesday after taking this photo. Seems like I remember seeing him scurry towards the crack under the baseboard and safety from the cat. Thursday, my new “friend” was on the ceiling in the sunroom. I nearly stepped on Carl on Friday. He was back on the floor, skittering towards the baseboard along the wall again.
Saturday, Carl was on the table in the sunroom. I decided to take a few more photos and I also decided that Carl might be getting hungry since I haven’t seen anything suitable for him to eat in the house. Also after reading about this species of spider, I understood it was possible he came into the house accidentally on some wood and might like it better if he was outside, but it was cold and rainy on Saturday, so I fixed him a nice spider hotel room for the night. He liked the view from the “balcony.” Sorry Carl, no room service available!
On Sunday after it warmed up a little, I took Carl down to our orchard. It was easy to coax him onto a twig. I held him up against a low branch on the apple tree and up he went. There was a veritable feast waiting for him in the apple tree. Tiny little morsels just the right size for a spider!
Some interesting facts about Coriarachne brunneipes, the black crab spider:
- Their coloring helps camouflage them perfectly on tree bark
- They don’t build webs, but wait perfectly still to ambush their prey
Interested? Read more about Crab Spiders here:
Taxonomy ~ http://www.americanarachnology.org/JoA_free/JoA_v2_n3/JoA_v2_p183.pdf