Robbie Hart discovered this beetle population on a sand bank at the far southern end of Lake Mills in Olympic National Park. Thanks to David H. Kavanaugh, Senior Curator of Entomology at the California Academy of Sciences, for the identification from a photo.

This species occurs on sandy, silty, and gravelly banks of medium to large streams all over western North America. The Elwha River forms a delta as it flows into this man-made lake. This environment will likely change in a few years, as the dam is scheduled for removal to reesatablish salmon runs. I have also photographed the same species on several occasions in 2007 and 2008.

These beetles move somewhat like Tiger Beetles (6), but fly less, and their large eyes resemble those of Tiger Beetles. On the same sandbank, I observed and photographed two species of tiger beetles (eg.: Oregon Tiger Beetle). While Opisthius looks somewhat like a small tiger beetle (both are members of the family Carabidae), its jaws are much smaller (photos 2 and 4), and, in my experience, it is more docile. I followed the individual in the movie (6) for several minutes, taking many photos, and often moving rocks to reveal it.

On one occasion, I photographed a mating pair (5). A cropped detail shows the sperm-transfer tube, the aedeagus. (See also Oregon Tiger Beetles mating)

We found the beetles somewhat difficult to photograph partly because of their 1 cm size and partly because the elytra are a satiny gray green that catches the glare of the sun and that the camera has a hard time focussing on. In the studio, I found it much better to use a very diffuse light, as in this photo. In the field, a diffusing shade helps. (Note that the black portion of the eye in photos 2 and 4 may be artifacts of drying.) The two specimens also carried commensal or parasitic mites, common on some beetles.

Photo 1 was taken by Robbie Hart with a Nikon Coolpix S4. All other photos on this page and the movie were taken by Stephen Hart with a Nikon Coolpix S10. I photographed the mating pair in mid May 2008. All other photos were taken in early to mid May 2007.