About Spiders As in the other arachnid orders, appendage specialization is very important in the evolution of spiders. In spiders the five pairs of appendages of the prosoma (one of the two main body sections) that follow the chelicerae are the pedipalps followed by four pairs of walking legs. The pedipalps are modified to serve as mating organs by mature male spiders. These modifications are often very complicated and differences in their structure are important characteristics used by araneologists in the classification of spiders. Pedipalps in female spiders are structurally much simpler and are used for sensing, manipulating food and sometimes in locomotion. It is relatively easy to tell mature or nearly mature males from female spiders (at least in most groups) by looking at the pedipalps -- in females they look like functional but small legs while in males the ends tend to be enlarged, often greatly so. In young spiders these differences are not evident. There are also appendages on the opisthosoma (the rear body section, the one with no walking legs) the best known being the spinnerets. In the first spiders there were four pairs of spinnerets. Living spiders may have four e.g., (liphistiomorph spiders) or three pairs (e.g., mygalomorph and ecribellate araneomorphs) or three paris of spinnerets and a silk spinning plate called a cribellum (the earliest and many extant araneomorph spiders). Spinnerets' history as appendages is suggested in part by their being projections away from the opisthosoma and the fact that they may retain muscles for movement
Much of the success of spiders traces directly to their extensive
use of silk and poison. Although most species do possess poison, the vast
majority are not dangerous to humans. These toxins are primarily for use against their prey -- other terrestrial arthropods. As a result, spiders are certainly among the
most important animals in controlling insect populations. In light of this, research is being done on ways to manage crops so as to encourage
spiders as an important means of pest control. Although all spiders use
silk, not all build webs to capture their prey. Additional material about web-building and hunting in spiders is presented in the five webpages featuring different groupings of spiders (see below).
Relationships Between Spider Groups The figure below depicts current thinking about the relationships between different spider groups as given in Spiders of North America -- An Identification Manual). Please note that the diagram has been simplified considerably. You can click on the GREEN lettered text items in the figure to go to other web pages for more information about the group or click on the photo links for each group (below).
Clicking on the photos below will take you to webpages that feature photos of spiders related to (or artificially grouped with) the one in the picture. Please note that all images are copyrighted by the person who submitted them. Further use beyond viewing requires the copyright owner's permission except as noted.
Useful World Wide Web Links to Resources That Deal With Spiders
- The World Spider Catalog, v2.0. by Dr. Norman I. Platnick of the American Museum of Natural History. It attempts to include "all descriptions of new species; .. all post-Roewer transfers or synonymies of previously described taxa; .. and all taxonomically useful (i.e., illustrated) references to previously described taxa".
- Nearctic Spider Database. Established in early 2005, this growing, on-line database provides species lists across North America, distribution maps, and the capability of searching for specimens. Contributions are made from institutions and individual collectors. The URL above takes you to the Canadian Arachnologist website. Access to and information about the database can be found there. You can also visit the on-line forum associated with the Nearctic spider data base.
- Spider Species List for North America: The name says it all; this work in progress represents a major undertaking by Rich Bradley and many other arachnologists.
- Common Names of Arachnids . -- A concordance of scientific and common names; download as pdf.
- The Tarantula Bibliography by Michael Jacobi, a well-done and complete website devoted to helping folks successfully keep tarantulas. Information about husbandry, natural history and a list of other resources.
- "Baboon Spiders" -- Theraphosids and "tarantula"-like spiders of Africa and the Middle East.
- Garden Spiders (Argiopes) of the USA
- California Jumping Spiders -- great photos and information on the evolution of the genus Habronattus
- The spiders of the Kaweah Oaks (CA) Preserve -- photos, natural history, check list.
- The Colorado Spider Survey: Information on the Colorado Spider Survey and a searchable database of Rocky Mountain spiders
- The Spiders of Kentucky: spider identification, interactive basic anatomy of spiders, U.S. species list, and a nice section on poisonous spiders.
- A Guide to Missouri Spiders -- nice photos and descriptions of some of the spiders found in Missouri and adjacent states. Also general information on spiders. Maintained by the Conservation Commission of Missouri
- The Ohio Spider Survey: The spiders of Ohio and more!
- Spiders and Arachnids (UC Riverside)
- Bites and stings of medically important arthropods (UC Riverside)
- Identification of the Brown Recluse
- The Hobo Spider Web Site
- South India Spiders -- a visually pleasing and very informative website dealing with spiders in general and specifically those found in southern India. Brought to all of the world by the Division of Arachnology in the Zoology Department at Sacred Heart College in Cochin, Kerala, India.
- Spiders of Northwest Europe
- Spider Conservation in the USA by Kevin L. Skerl
| The AAS publishes a very useful manual for anyone with more than a passing interest in spiders. Entitled: Spiders of North America -- An Identification Manual -- it presents general information about spiders, about the families of North American spiders, and a scientific identification key to the genera of North American spiders. A must have for any serious amateur or professional.
This photo gallery is brought to you by members of the AAS and other arachnologists.
The AAS wishes to thank the College of the Holy Cross for hosting this site.
last modified November 27, 2009