ITIS Weaves Enhanced Coverage for Spiders of the World
| Taxonomic Hierarchy
In recent issues of Access we talked about the Integrated Taxonomic Information System (ITIS) being in the midst of a large, continuing effort to update its plant names. Subsequently, Access explored the major ITIS effort to expand its coverage of another important taxonomic group: beetles (order Coleoptera).
Since good things often come in threes, the ITIS version of that maxim has taken shape in the much underappreciated taxonomic group: spiders (order Araneae). USGS and its ITIS partners have recently added the spiders of the world to the system. Which is to say, lots and lots of spiders! The update was based upon the 2011 World Spider Catalog by Norm Platnick and included 46,353 new and edited scientific names.
This comprehensive list includes scientific names and associated data for spiders that are listed as endangered under the U.S. Endangered Species Act, and at risk species that are traded internationally and monitored under the Convention on International Trade in Endangered Species of Wild Fauna and Flora. Also included are species of interest in State Wildlife Action Plans. The addition of spiders is a significant advance, pushing ITIS to over 600,000 scientific name records.
Spiders and other arachnids like harvestmen, scorpions, ticks, and mites are an ancient group quite different from insects. Unlike insects, they have two, not three, body regions and eight, not six, legs. Spiders invaded land independently from insects hundreds of millions of years ago and now constitute the 6th most diverse order on Earth, with 109 families, over 3,800 genera, and more than 41,000 species described to date. Still, many tens of thousands of species remain to be discovered and described.
Spiders are voracious predators. Spider numbers can reach millions per acre, so collectively they eat billions upon billions of insects. These predators can also be quite adept in discerning their favorite insect prey. A recent study showed that Evarcha culicivora, an East African jumping spider that forages on mosquitoes, visually distinguishes differences between male and female mosquito antennae to selectively eat female blood-fed mosquitoes. The same study also showed that the spider can cue on the abdomen, head, and thorax of mosquitoes to assess whether the mosquito is meal-worthy, suggesting the decision to strike out for an individual mosquito in a swarm of potential prey is accompanied by rapid processing of much optical information.
Photos courtesy of Dr. Jonathan A. Coddington, Smithsonian National Museum of Natural History.
Spiders are famous for their silk, which, unlike all other silk producing animals, they use throughout their lives. Spider silk is the toughest fiber known because it can absorb so much energy before it breaks. Consider, for instance, how their webs are able to withstand the strike of a flying insect when it encounters a web at speed. Now researchers at the Massachusetts Institute of Technology studying the silk and webs of Nephila clavipes have revealed that not only is silk very strong, but its mechanical properties create very damage-resistant structures. The way spider silk strands interact with each other when they stretch and then become stiff again keeps damage to parts of the web localized. If material scientists can replicate this damage resistance in human-engineered construction, it will result in stronger and more damage-resistant products like bridges and bullet-proof vests.
Even though they control insect populations and can teach us how to engineer materials to avoid catastrophic break-up, negative notions of the spider persist. The reason may be that all but a few spiders use venom to subdue their prey. However, relatively few spiders—only species in four genera—seem to be dangerously venomous to humans. And spider venoms can be beneficial to society, with venoms currently being evaluated as novel insecticides and as treatments for diseases such as breast cancer and heart disease.
ITIS provides an easily accessible database with reliable information on species names and their hierarchical classification for the world's biota, giving priority to North America. A partnership of Federal agencies, international partners, and non-government organizations led by the USGS and hosted by the Smithsonian Institution, ITIS can be accessed at http://www.itis.gov.
Cranford, S. W., Tarakanova, Anna, Pugno, N.M., and Buehler, M.J., 2012, Nonlinear material behaviour of spider silk yields robust webs: Nature, v. 482, p. 72–76.
Nelson, X. J., and Jackson, R.R., 2012, The discerning predator: decision rules underlying prey classification by a mosquito-eating jumping spider: The Journal of Experimental Biology, v. 215, p. 2255–2261.
This article was shaped heavily from consultation with Dr. Jonathan A. Coddington, Curator of Arachnids & Myriapods in the Department of Entomology, Smithsonian National Museum of Natural History.