Tuesday, September 13, 2011

Lions, Tigers, and ORB SPIDERS, OH MY!

With BugFest coming this weekend to Raleigh's Museum of Natural Sciences, we found it appropriate to have a short posting on spiders, specifically orb spiders.  For those of you not familiar with BugFest, it is an annual festival that celebrates all things creepy and crawly! Each year, the festival has a different theme, with this year's theme being SPIDERS.  David Stephan, the Plant Disease and Insect Clinic's resident entomologist, prepared the following post on orb spiders, a common group of spiders found throughout North Carolina.  

Orb Spiders

Spiders are among the most maligned and misunderstood creatures on Earth.  These fascinating arthropods are mostly beneficial to humans as predators of insects and other pests, but the few that are genuinely dangerous to us have given all spiders a bad rap.  Almost all spiders are venomous (except for the species in one obscure family), and almost all are predators.  Very few species are truly aggressive, most opting to freeze or flee in encounters with people.  All spiders produce silk, and many of them use this silk in various ways for prey capture, construction of retreats, courtship, protection of their eggs, etc.

Orb spiders of the family Araneidae are among our largest and most beautiful spiders (oh yes they are!).  They spin those large, radially symmetrical webs that people often find in their yards from mid summer into fall.  Outdoor lights and windows attract many insects, which makes them popular sites for orb spiders and others to spin their webs.  The spider may wait in the center of its web, or in a hidden retreat nearby, ready to rush out and wrap prey that fly into the web.  Most adults will die by winter, after preparing 1 or more sturdy egg cocoons.  Orb spiders are timid and avoid contact with people, but blundering into one of their webs in the dark could give you a heart attack.

Golden Silk Orb Spider, Nephila clavipes
(Photoby David Hillquitst, Bogue Banks, NC)

Our largest NC orb spiders belong to the genera Araneus, Argiope, Neoscona and Nephila.  The mostly tropical species of Nephila include the world’s largest orb spiders, and can build spectacular webs.  The silk that spiders produce has amazing properties of tensile strength and extensibility, and scientists have been studying it for many years.  Researchers in the College of Textiles here at NCSU have worked with orb spiders in the past.  Currently, researchers in our Dept. of Chemical & Biomolecular Engineering are using the latest technology to study, duplicate and even improve on some of those properties of spider silk. 

Golden Silk Orb Spider, Nephila clavipes
(Photoby David Hillquitst, Bogue Banks, NC)

Not enough spider info to satisfy your appetite? Be sure to visit BugFest, Saturday September 17th.  NCSU Departments of Plant Pathology and Entomology have displays with even more info about spiders!

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Special thanks to David Stephan for contributing this post!