|Jumping Spider - Habronattus decorus|
Family Salticidae - Jumping Spiders
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Live adult jumping spiders photographed in the wild at Edina, Minnesota.
Genus Habronattus is a large diverse genus of medium-sized salticids, primarily ground-dwellers and with highly ornamented males that perform complex courtship displays. Approximately 100 species are known, most from North America, the remainder in the neotropics. Most are ground-dwelling on open ground with sparse vegetation, especially on rocks, dry leaf litter and sand. The arid southwest has many species, but Florida also has many species, and others are known above the Arctic circle and east to maritime Canada.
Identification: The elbowed tegular apophysis ("conductor") of the palp is distinctive. The third leg is much longer than the fourth, distinguishing these from other superficially similar genera such as Sitticus. The epigynum has a triangular or tubular guide. 
|Jumping spider's anatomical points of interest:|
Jumping spiders have excellent vision, among the highest acuity in any invertebrate. The eight eyes are grouped four on the face 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. 
Note: the function of the posterior medial eyes is unknown 
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 sits on top of the eyes and brain. 
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. I am continually amazed at the resourcefulness of these supremely successful predators.
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