Monday, February 20, 2017

Jumping Spider

Silk under the bark

This time of year it is hard to find new subjects in nature so I was pleased to find a new spider when out hiking with Mark Bower.  He found this when he stripped bark off a dead tree in search of fungi. "When I stripped off the bark, part of a web was wiggling, and I had to kind of squeeze the spider out." This species uses silk to cover its eggs and also to create a winter home for itself.

Metallic chelicerae of a Phidippus species
After chasing it around in a coffee cup with my camera, I gave up and cooled it in the fridge before finally getting good pictures.  The bright metallic blue- green chelicera are a sign of  the genus Phidippus.  It has the large anterior medial eyes typical of Salticidae.  This is the Canopy Jumping Spider, Phidippus otiosus, which can be found from North Carolina to Texas.  Females lay eggs in the winter, positioning a single egg sac under the bark of oak and pine trees.

Jumping spiders are favorites of collectors and you can even buy them online.  Their popularity is partially based on their eye placement, giving them a distinctive face.  Their large eyes seem to study their surroundings with apparent intelligence including to appear to focus on our faces when viewed closeup.*

The coloration of the spots on the dorsal abdomen of P. otiosus vary from white to red on available pictures.  In general, colors can vary a lot between individuals but the pattern of spots on the back of the abdomen is a common feature.*  Many of the Phidippus species have sophisticated hunting strategies.
"Like most spiders, jumping spiders have 8 eyes arranged in a characteristic pattern with two large anterior medial eyes in the center.  Extensive studies in the 1960s described the eyes in detail.
Jumping spiders, also known as salticids, alternate between entertaining and alarming us by planning prey-capture tactics ahead of time, adjusting their hunting behavior in accordance with how the prey responds and giving us other examples of un-spider-like acumen.  (Harland and Jackson, 2004).
Underlying salticid behavior, there is a more basic defiance of common sense. We may think that spider-size eyes are simply not suitable for seeing a lot of detail, but salticids seem to be telling us to think again. Here we have a celebrated example of how seeing with high spatial acuity can be achieved at a high level by a lowly animal working under severe size constraints. " Jackson and Harland.
* Common Spiders of North America, Richard Bradley, 2013

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