Weekly Invertebrate Blogging - Four Five of A Kind

Today's spider post is a winning hand - four five of a kind if you're counting families (Araneidae), or two pair if you're counting genera (Argiope and Araneus).

A. Argiope trifasciata	B. Argiope aurantia
C. Araneus diadematus	D. Araneus sp. (marmoreus?)

The family Araneidae are often referred to as orb web spiders or wheel web spiders. Three of the four orb weaver photos above (A, B, and D) were taken at my in-law's farm in Washburn, Tennessee last week. The "banded garden spider" (A) and the "black and yellow garden spider" or "writing spider" (B) were found within two meters of each other on the same fence!

Regular visitors might recognize spider C as the same type of spider as the "backyard Shelob" I posted about a few weeks ago. While spiders of the genus araneus and related genus neoscona are difficult to distinguish, I'm fairly confident that "Shelob" is A. diadematus (aka "European Garden Spider"). This spider is often called the "cross spider," because of the distinctive cross-shaped pattern on the back of its abdomen. The patterns on these spiders can vary widely, but they are unmistakable. Brooklyn is is positively rife with these spiders. It is virtually impossible to walk down any block in Park Slope without seeing one of these lurking in the hostas by someone's front stoop.

The last spider was found roosting in the eaves of my in-law's barn. It may be an A. marmoreus, or "marbled orb weaver."  This spider's observed behavior was different from that of the other three. I observed that it it spent just as much time out of its web as in. It also seemed to be more active at dusk, whereas the other spiders spent all day in the middle of their web and were observed feeding all day. Then again, as I've stated before, I'm not an arachnologist. We saw a similar spider under the deck of the cabin we stayed in two weekends ago in Highlands, North Carolina. That spider was only seen in the center of its web at night.

One thing I've noticed about most orb web spiders is that they have spiny legs. Click on the pictures to enlarge them to see what I mean. I'm not sure what function the spines serve - transmission of vibrations? stability? decoration? Who knows? (yeah I know, The Shadow probably knows, but he doesn't visit this blog)

*SPECIAL BONUS SPIDER*

Lecauge sp., the "Orchard Spider"

While I was googling for information on orb weavers I came across a familiar image - a small yellow and black spider with elongate front legs and a characteristic web "stance." I had been photographing these delicate little spiders in Prospect Park since early spring, but I had no idea what they were. At the risk of revealing my arachnological ignorance, I assumed they were immature writing spiders and kept waiting to find a big one. I eagerly awaited the growth of one specimen that lived just outside my client's office in White Plains. After several weeks of bringing my camera for lunch hour photographs, I realized that this was a different species, but I hadn't a clue how to find out what it was. The spider guides available in bookstores and libraries are way too general to be helpful.

Photographing these little guys was always frustrating, because the webs, while beautiful, were nearly always parallel to the ground and slung in low vegetation such that steadying oneself was difficult. Even with a tripod, the shape and delicacy of the webs made them very vulnerable to movement in the breeze (This is even a problem with larger webs, the shakiness in photo C above is due to wind movement, the bane of spider photographers everywhere). These pictures aren't great, but I think you get a since of just how elegant and colorful these often overlooked gems are.

If you're an arachnophile, you'd better get out there soon. This is probably the last decent month for outdoor spider spotting, at least in New York. If you're fortunate enough to have some free time when we have those deep azure October skies, the late afternoon light provides some nice photo ops.

For more candid camera critters, visit the Friday Ark.

Click here to scroll through my entire invertebrate portfolio. What a long, strange, spineless trip it's been.

Comments

[persimmon]

I believe the spines are tactile sense organs. Typically, they are articulated and ennervated. Orb weavers need good sensory perception for wrapping prey. Even if their eyes were sensitive enough to be of help, they are on the wrong side of their body with respect to prey capture. Most likely, their visual acuity is too crude anyway.

Their courtship rituals include a lot of leg-waving. Also, spiders have delicate sensory hairs called trichobothria, and stiffer spines may help protect those hairs. Trichobothria are sensitive to airborne vibrations like wind and sound, and they are especially abundant in wolf spiders.

Great photos!