Jumping Spider - Thiodina Sylvana
Family Salticidae - Jumping Spiders
Live spiders photographed at northern Illinois.
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Jumping Spider - Thiodina Sylvana
This is a large male jumping spider at 10mm. He was out hunting for prey and females in the leaf-litter on the forest floor at Castle Rock State Park in Illinois, along the banks of the Rock River. I was only able to follow him for a short while - as soon as they notice you watching, they almost always become surreptitious in their movements.

Jumping spiders are small to medium in size, stout-bodied and short-legged, with a distinctive eye pattern. The body is rather hairy (pubescent) and frequently brightly colored or iridescent. Some species are antlike in appearance. The jumping spiders forage for their prey in the daytime. They approach prey slowly and, when a short distance away, make a sudden leap onto the unfortunate animal. They are good jumpers and can leap many times their own body length. [3]


This is a large adult male at 10mm [1]
Jumping spider's anatomical points of interest:
  • Esophagus passes straight through the brain
  • Portion of gut overlies the eyes and brain inside carapace
  • Heart extends from abdomen into cephalothorax
  • Leg muscles attached inside the carapace operate legs like marionette puppets
  • Jumping spider's brain volume to body size proportionate to human, but visual processing region is larger
  • Salticids move retinas inside the eyes to look in different directions, as the lenses are fixed in the carapace
External Spider Anatomy
External Spider Anatomy
A. Dorsal (top) view       B. Front view of face and chelicerae      C. Ventral (bottom) view (some legs omitted) [4]

The male prepares to mate by spinning a small web and depositing a drop of sperm on it from the underside of his abdomen. He then places the tip of his palpus into the sperm, and draws the sperm through the palp's opening into the sperm duct where it is stored. He then goes cruising. If he finds a female, he performs a courtship dance for her, during which she assesses his fitness. If she accepts him, he places his palp against an opening on the underside of her abdomen (her epigynum), and guides it into place by putting a thumb-like projection, the tibial apophysis, into a groove in her epigynum. The palpus then expands, locks in place, and injects the sperm. [3]

References
  1. Bugguide.net, Jumping Spider - Thiodina sylvana
  2. Jumping Spider Vision David Edwin Hill, licensed under the Creative Commons 3.0 Unported 
  3. Maddison, Wayne. 1995. Salticidae. Jumping Spiders. Version 01 January 1995
  4. William J. Gertsch, PhD. "American Spiders"
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