Ozyptila praticola In Tree Trunk Moss On The Cedar River

Site location map. Pins and circles indicate moss and cardboard
trap samples, respectively. Blue, yellow and red markers
indicate adult O. praticola, juvenile O. ?praticola, and no
O. praticola found, respectively.

My ongoing search for the outer edges of the local range of the introduced European spider Ozyptila praticola (Thomisidae) brought me recently to the Cedar River. This spring, I set out cardboard live traps at five locations along the Cedar River between 154th Place SE in Renton and Landsburg Road in Ravensdale, and later collected juvenile Ozyptila probably-praticola from traps at two of them. To confirm which species of Ozyptila was present, I re-set traps or sifted tree trunk moss at thirteen river valley sites between the Interstate 405 overpass in Renton and Landsburg Road in Ravensdale. Logistical constraints dictated which collection method I used.

Female Ozyptila praticola sifted from
tree trunk moss at Habenicht Park

To date, I have found mature O. praticola from the I-405 overpass to as far upstream as Fred V. Habenicht Rotary Park in Maple Valley (blue icons on map, above). Upstream of Habenicht Park, the only mature Ozyptila I've collected were the native O. pacifica. Notably, I didn't find O. pacifica at Habenicht Park or any site downstream from there. As I've mentioned before, I've never found the native O. pacifica and the introduced O. praticola present at the same location.