Jumping Spider - Phidippus clarus

Jumping Spider - Phidippus clarus
Family: Salticidae
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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

Swollen palpi = male spider

Male spiders have an unusual way to get sperm into the females: they use their palpi, the little 'feelers' beside the face. In the females, these palpi are simple and leg-like. Spiders use them like little hands, to manipulate food and clean their faces. But adult males have the palpi swollen and more complex.

When the male is ready to mate, 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. There 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, the tibial apophysis, into a groove that is usually at the back of her epigynum. The palpus then expands and injects the sperm into the female.

Phidippus male keeps a close watch on me. The long forelegs are adapted for rapidly capturing prey.

Female with ambush bug prey

References

Bugguide.net, Phidippus clarus
Jumping Spider Vision David Edwin Hill, under the Creative Commons Attribution 3.0 Unported

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