27-April-2018 Tacoma, Washington

Site location map. Click to enlarge.

I was very happy when Rod Crawford and I were invited to participate in Point Defiance Park BioBlitz 2018. The park's 760 acres of mature forest, shoreline habitats, zoo and botanical gardens caps the north end of the peninsula that is Tacoma, and is usually closed to collectors. Participating in the BioBlitz allowed Rod and me to explore the spider fauna of this gem to the benefit of both the park and the Burke Museum, while also giving me another opportunity to search for the introduced European crab spider Ozyptila praticola (Thomisidae).

And speaking of O. praticola, on our way to the park, Rod and I made a brief stop at University of Puget Sound to check a live trap that I'd placed there the week before. I had hoped it would contain mature O. praticola, proving the presence of the species that I'd so far only collected there as juveniles. Alas, it wasn't to be; the trap was empty.

Rod sifts leaf litter at Owen Beach as
one of our very helpful high school senior
assistants inputs IDs into iNaturalist.

We spent a good part of our day in the park collecting at Owen Beach. This location gave us access to numerous habitats, including shoreline conifers, understory vegetation, tree trunk moss, buildings, and leaf litter.

Antrodiaetus sp. juvenile

Many specimens were of course too tiny to identify in the field for BioBlitz purposes, but we were able to find some exciting larger specimens for our assistants to photograph and input into the iNaturalist database. This folding-door spider (Antrodiaetus sp., family Antrodiaetidae), for example, was one of the more photo-worthy spiders I sifted from moss.

Cone source in the native plant garden.
The Meadow is to the left.

After we completed our work at the beach, a field assistant very helpfully directed us to the park's Northwest Native Plant Garden as a place where we might find uncut grass to sweep. (The other potential location, the zoo's muskox paddock, didn't sound like a wise choice...) While Rod swept "The Meadow", I tapped 100 fallen Douglas-fir (Pseudotsuga menziesii) cones from the bordering stand of young trees that had apparently been planted as a buffer zone.

Cybaeus sp.

Cybaeus exuvium (center) and
spider (arrow)

All that cone tapping only produced eight spiders, but three species were identifiable. One of them, Linyphantes nehalem (Linyphiidae), we didn't collect in any other microhabitat this day, nor had I ever tapped it from cones before. Less interesting for the species list, but certainly interesting from an ecological perspective, was this teneral juvenile Cybaeus (Cybaeidae) and its exuvium. It had used the cone as a molting place.

Lots of cones in the parking
lot border

Open cones in lush litter

By this time I was pretty tired, and my stomach was beginning to rumble for the promised BioBlitz taco bar. But I couldn't bear the thought of not tapping the fallen black pine (Pinus nigra) cones I had noticed on our drive from Owen Beach to the native plant garden. Black pines were among the row of conifers that had been planted as a visual barrier between the main parking lot and a maintenance yard, and they had dropped a lot of cones. I again tapped 100 cones and again found few spiders -- this time only six. In contrast to the cone spiders from the native plant garden, however, of the two species identifiable here, the one we didn't find in any other microhabitat this day was the very common introduced species Tenuiphantes tenuis (Linyphiidae). Among spiders identifiable to species, I've found T. tenuis at more cone sampling sites in western Washington than any other species except O. praticola.

You can read Rod's take on the day here.

As afternoon shifted towards evening, black-tailed deer
(Odocoileus hemionus columbianus) began appearing.