This is a dolomedes fishing spider. A very happy, about to be well fed, fishing spider who has neatly removed the head of an unfortunate dragonfly. You may better know this spider as a raft spider, a wharf spider, or (more popularly) as a dock spider. These spiders are amazing creatures... they are able to walk on water (much like a water strider) where they are able to hunt mayflies, aquatic insects and even small fish. They even have the ability to hunt underwater! This particular spider was an excellent dragonfly hunter, as I found him with another unfortunate dragonfly victim the following week.
|A female fishing spider with spiderlings. |
When it comes to identifying spiders, there are several things you can look at to help figure out what you're dealing with. Size, colour, special markings, etc. When it comes to the fishing spider, one of my favourite ways of telling what I have is by looking at the eye pattern of the spider. For the fishing spider, I look for two rows of 4 eyes stacked on each other like little smiles. I have cropped and enlarged two photos to show the pattern. My apologies for the quality, but cropping and enlarging compromises photo quality.
Two rows of 4 eyes.
Here is a link to Bug Guide that takes you a page showing all the different eye patterns of different spiders: http://bugguide.net/node/view/84423
I no longer find it so difficult to find fishing spiders. There is a little creek that feeds into the lake near my house. Every summer I am easily able to find dock spiders in the tall grasses that grace the banks of the creek - and then I take plenty of photos to share with family and friends!