The scientific term for the widow spider is a member of the spider genus Latrodectus. The majority of the Latrodectus genus in and of itself breaks down taxonomically into approximately 31 recognized species, with the family Theridiidae (black widow spiders, also known as tangle-web spiders) as its most well-known group.

The classification of the Latrodectus genus also includes the Latrodectus mactans, inhabitant of North America. Along with the Latrodectus mactans are the gray widow spider (classification Latrodectus geometricus), Latrodectus bishopi, Latrodectus variolus as well as Latrodectus hesperus or western widow (Preston-Malfham, 1998).

Commonplace to Latrodectus growth is the shedding of their chitin shells (a process of molting). Arthropods also possess an open circulatory system by which blood is pumped directly from the heart of an organism throughout its body cavity, bathing the internal organs of said organisms directly with hemolymph—a combination of digestive nutrients and blood (Encarta, 2004).

As far as environments go, a few species of the Latrodectus genus live in tropical environments, while others such as the Latrodectus mactans occupy areas of areas of aridness along with the species of Hesperus who inhabit much of the American deserts (Preston-Malfham, 1998). As it is of a tropical, Mediterranean type area where these spiders live, or scorching deserts, the climate often ranges from moist, and many times humid--due to the evaporation of rain—to parched and desiccated.

Of the latrodectus feeding style, widow spiders are primarily of an ambushing, sneaking and trapping mentality. In general, spiders feed on live insects, but many avoid ants, bugs, and certain beetles; woodlice and millipedes are also unpopular (Hillyard, 1994).

Female spiders also have an epigynum (genital opening) on the underside of the abdomen, with the males possessing pedipalps attached to each side of the spider’s mouth; both have openings to the breathing organ called a book lung (Discovery Books, 2000).

The world-famous black widow spider, Latrodectus mactans, has a prominent red hourglass figure on the bottom of its abdomen. Many of the other widow spiders have red patterns on a black or dark background, a clear warning that they are not to be trifled with. Some of the more well known species of widow spiders are listed below, together with some of the areas where they are found. This list should not be considered complete.

• Latrodectus geometricus Africa, U.S.A.
• Latrodectus curacaviensis Americas
• Latrodectus geometricus South Africa
• Latrodectus hasselti the red-back spider, Australia
• Latrodectus hystrix S Europe, N Africa, SW Asia
• Latrodectus dahli S Europe, N Africa, SW Asia
• Latrodectus hesperus western US
• Latrodectus indistinctus S. Africa
• Latrodectus lugubris in Kazakhstan and Central Asia
• Latrodectus mactans, the black widow spider, warm regions of the U.S.A.
• Latrodectus pallidus S Europe, N Africa, SW Asia
• Latrodectus rhodesiensis, South Africa
• Latrodectus tredecimguttatus Mediterranean area
• Latrodectus bishopi Florida, USA
• Latrodectus variolus Florida, USA

Sources

• Discovery Books; 2000; Insects and Spiders; St. Remy Media Inc.; New York; 35
• Freeman, Scott; 2003; Biological Science; Prentice-Hall
• Hillyard, Paul; 1994; the Book of Spiders; Random House, Inc.; New York; 47-50
• Hillyard, Paul; 1994b; The Book of the Spider; Avon Books; New York; 22-25
• Martin, Louise; 1988; Black Widow Spiders; Rourke Enterprises, Inc.; 18-20
• Preston-Malfham, Ken; 1998; Spiders; Chartwell Books; Edison; New Jersey; 40.
• "Arthropod," Microsoft® Encarta® Online Encyclopedia 2004