Excerpts from Jim Conrad's
from the August 2, 2009 Newsletter, issued from the Siskiyou Mountains west of Grants Pass, Oregon:
Up at the pond one you see Water Striders (insects, thus not spiders, which are arachnids) skating across the water's surface, as shown above.
Basically you see water striders doing two things. You see them prowling across the water's surface looking for prey, traveling about five ft/second, or 1.5 m/second. If you flip a tiny bit of wood onto the water they'll jump on it with lightning speed. Second, you see them mating. One strider skates past the other and with the same quickness suddenly one mounts the other. It all happens so fast that you wonder how they can know what sex the other is.
Researchers have looked into that question. They placed little masks on male water striders so they couldn't see (!) and found that if they caused female water striders to issue computer-generated surface- wave and body-contact signals of about 90 waves per second, typical of males, the females were treated as males. Just think of the sensation of the water you're skating on feeling alternately masculine and feminine. An abstract of that research paper is available here.
Water striders stay atop the water because of the water's surface tension and because they have "hydrophobic legs" coated with wax. They paddle forward with the middle pair of their legs, using their fore- and hind legs as rudders.
I'm guessing that the individual in my picture is GERRIS REMIGIS because it looks like other images of that species, and that species is a very common one. However, in the Water Strider Family, the Gerridae, about 500 species are recognized in about 60 genera, so who knows whether it might be a look-alike relative?