Last week I went to Seattle with Ryan for a family reunion. We spent Thursday afternoon exploring the Washington Park Arboretum, a very pretty park containing all sorts of exotic-looking plants, including magnolias, asiatic maple, rhododendrons and camellias. It didn’t take long to notice that the vegetation supported many spider webs, and that the abundance of spiders was noticeably higher than in Logan.
Washington Park Arboretum
The first spider I found was an araneid of the genus Zygiella, an exciting find since I had never photographed this genus before. Zygiella spiders have a relatively flat, oval abdomen, and eyes that are closely spaced. The back of the abdomen has a leaf-shaped pattern (folium) that is generally white in the front and dark in the back. The orbweb built by adults is interesting because it typically has a missing sector on the upper half, in the direction of the spider’s retreat. The missing sector is where the safety line is located, and this thread leads from the hub of the web to the retreat, as seen in the pictures below.
Zygiella close to her retreat
Zygiella leaving her retreat to go on the safety line
Not far from the Zygiella web, I noticed a silk tent under which a small spider was guarding her eggs, which she kept in a round sac. I only got one picture and did not try too hard to identify her as I didn’t want to disturb her .
A female web spider guarding her eggs
A tangle-web under a leaf revealed a theridiid (probably in the genus Theridion) with a branching pink median stripe on the back of its spherical abdomen. This spider reminds me of Theridion pictum, a species that is found in Europe, North America and Africa.
The most conspicuous spider in the park was the Cross Orbweaver, Araneus diadematus. The webs of this spider were everywhere, even outside the park, in people’s yards. This is the same species than the one mom found in our yard in France (see previous post).
I found a tetragnath spider of the genus Metellina, sitting in the center of a web, in a shrub relatively low above the ground. Tetragnaths, which are also known as Long-jawed Orbweavers because of their typically long chelicerae, build orbwebs that have a “hole” in the center. Their webs do not have a safety line or a retreat as described for the araneid Zygiella. There are only three species of Metellina in North America. The one I found was probably Metellina segmentata, a species introduced to Canada from Europe and first found at the northern edge of Washington in 1986.
The underside of Metellina
, sitting on the empty hub of her web
As I was walking by some vegetation low on the ground, I noticed that most of it was covered in sheets of silk. I took a closer look and found that these were funnel-shaped webs built by spiders in the family Agelenidae, which are also known as Funnel-Web Spiders. The notorious Hobo Spiders belong to this family. These spiders usually sit inside a funnel-shaped retreat, but when they detect the vibrations caused by trapped prey, they quickly run across the sheet of silk to bite the victim. I tried to get one of these spiders out of its retreat by gently poking the sheet web. The spider came out so quickly that it startled me!
Agelenid spider waiting inside the funnel of its web
The agelenid runs out in response to vibrations in the web
Ryan found a philodromid spider on a bench, at the base of the armrest. Philodromids are active hunters that do not rely on webs to catch prey. This spider appeared to be guarding her eggs, which she had covered in a protective layer of silk. She did not move away from her eggs, even when I got very close to take a picture.
Even benches can provide good habitat for spiders!
Philodromid spider guarding her eggs
I was excited to find the spider below in the rolled-up leaf of a shrub, although it is a species introduced from Europe. The spider belongs to the family Theridiidae, and the species is Enoplognatha ovata, a spider with yellow-white legs that varies alot in color and pattern. This individual had two pink stripes with small dark spots, on a cream-colored abdomen.
In a shrub nearby, I barely noticed a tiny tetragnath spider, holding onto the underside of a leaf, its long and slender legs stretched out in an attempt to blend in with the nearby vegetation. Many members of this family are characterized by these very long legs.
A small tetragnath resting under a leaf
After walking under a bridge to get to the other side of a busy road, I inspected the outside walls of the bridge and found a couple of big Larinioides sclopetarius sitting in their webs. This spider, also known as the Bridge Spider, or Gray Cross Spider (family: Araneidae), prefers to build its web on man-made structures, especially near water. Apparently, it is rarely found on vegetation. In both sexes, the cephalothorax has conspicuous white markings, as seen in the picture below:
Larinioides sclopetarius on a bridge wall