Swimming after dark in our pool is currently an adventure, because we’re not the only ones in the water. The local Coast Guard makes frequent forays across the shipping lanes, issuing from his snug berth in a cavity between the edge-tiles at the shallow end.
Here is the Coast Guard himself:
He’s a sizable male Six-Spotted Fishing Spider (Dolomedes triton, photo A.Shock). We think he’s male because of his trim abdomen and long leg-to-body ratio. And sizable as in “would-sit-on-the-palm-of-your-hand-with-only-a-little-to-spare.”
We’ve always had these handsome but intimidating spiders living around our pool — one, sometimes two at a time, each at opposite ends — holed up during the day and visible only as hair-thin leg-ends curled subtly around the edge of a cracked tile inches above the water. At night, however, they hunt, either hanging by their back legs with their sensitive front legs spread across the water, waiting for a surface-trapped insect to struggle by, or by speedily skittering across the taut surface, gleaning the day’s “tar-pit” casualties.
Fishing spiders are intensely aquatic, and will catch and eat anything they can subdue, including small fish — an item not on the menu in our pool, but there’s plenty of small invertebrates to feast on. The Coast Guard clearly finds plenty of nourishment: he’s grown quickly since we first noticed him earlier in the warm season.
Six-spotted Fishing Spiders are common water-side natives of Arizona and much of the United States. And in case you’re wondering, his eponymous spots are on the underside of his cephalothorax, but I’m not flipping him over to count!