Jumping Spider - Phidippus clarus
Live adult jumping spiders  photographed at northern Illinois. Family Salticidae - Jumping Spiders
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Jumping Spider - Phidippus clarus

P. clarus out and about hunting.

Jumping Spider - Phidippus clarus

You want a piece of me?

Jumping Spider
Swollen palpi = male spider
Male spiders have an interesting way of inseminating a female: they use their palpi, the little 'feelers' beside the face. In the females, these palpi are simple and leg-like.  But adult males have the palpi swollen and more complex.

He spins a small web and deposits a drop of sperm on it from the underside of his abdomen. He then places the tip of the palp into the sperm, and draws the sperm through the palp's opening into the sperm duct of the palp, where it is stored. The male then goes out in search of females. If he finds one, he performs a courtship dance. If she accepts him, he places his palp against an opening on the underside of her abdomen (her epigynum). He locks it in place by putting a thumb-like projection into a groove in the back of her epigynum. The palpus then expands and injects the sperm into the female.
 

Jumping Spider - Phidippus clarus

Jumping spiders have excellent vision, among the highest acuity in invertebrates. The eight eyes are grouped four on the face (the two big anterior median eyes in the middle, and two smaller anterior lateral eyes to the side), and four on top of the carapace. The two large, forward-facing eyes (AME) are tubular behind the lens, with a well-developed musculature, unique to salticids, that supports and moves the retina - the opposite arrangement of our own eyes. [1]


Note: the function of the posterior medial eyes is unknown [2]

Spider musculature is also different from ours: in the spider, muscles operate from the inside to move external skeletal elements; our own skeletal muscles surround the elements they operate. But even these glaring differences are nothing compared to the jumping spider's brain and digestive system - their esophagus passes right through the brain, and one branch of the gut (analogous to our intestines) actually overlies the eyes and brain! [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
References
  1. Bugguide.net, Phidippus clarus
  2. Jumping Spider Vision, David Edwin Hill, via Creative Commons Attribution 3.0 Unported
  3. Arthur V. Evans, National Wildlife Federation Field Guide to Insects and Spiders of North America
  4. Clark Kimberling, University of Evansville, "Thomas Say, Father of American Entomology"
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Class Arachnida / Order Araneae: Spiders are the largest group of arachnids.  They are easily recognized by their eight legs, and there are few creatures great or small that elicit such irrational fear in mankind. The vast majority of spiders are completely harmless and offer beneficial services, chief of which is keeping the burgeoning insect population in check. Spider Index | Spider Main | Funnel Web
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