A terrestrial environment is the habitat of the. It is ubiquitous and builds strong-walled retreats quite close to the ground and in dark sheltered spots. However, it also spreads its snares over plants. Webs of the black widow spider can be found in recesses under stones or logs in a woodpile, in crevices or holes in dirt embankments, in barns and outbuildings. They can also be found around lids of dust bins, around seats of outdoor privies, spaces under chips of wood, around stacked materials of any kind, in deserted animal burrows or rodent holes, and entwined in grape arbors. This spider may find its way into clothing or shoes and occasionally seeks a spot in a house to build a web, but it is usually not found indoors. When it does seek shelter in a building, it is due to cold weather and a need for a dry shelter. In addition, in the eastern United States, is associated with littered areas, with dumps of large cities, with garages, and storage sheds. In arid parts of Arizona, this spider inhabits almost every crevice in the soil and its nests are found in cholla cacti and agave plants. (Ferrand, 1988; Kaston, 1953; Preston-Mafham, 1984; Comstock, 1948; Gertsch, 1979; Shuttlesworth, 1959; Snow, 1970; Smith, 1980; Emerton, 1961; “Black Widow Spider, www.nscu.edu)
Biomes: temperate and tropical zones, including temperate forest, tropical rainforest,
temperate grassland, chaparral, desert
is the largest spider of the family Theridiidae. The black widow spider is shiny, coal black in color. The female averages 8-10 mm in length and has long slender legs and a round abdomen. Usually on the underside of the female’s abdomen (venter) is a red hourglass mark and one or two red spots over the spinnerets and along the middle of her back. The male is 3-4 mm long with an elongated abdomen. The male’s legs are larger than the female’s and each joint is orange brown in the middle and black on the ends. On the sides of the male’s abdomen there are four pairs of red and white stripes. Young spiderlings, or juveniles, are orange, brown and white; they acquire their black coloring with age, or with each molt. (Emerton, 1961; Milne, 1990; Comstock, 1948; Kaston, 1953)
Another important characteristic ofis its “comb foot.” The spider has a row of strong, curved bristles on the hind pair of legs, which form a distinct comb. The comb is used for flinging silk over its prey. (Shuttlesworth, 1959; Comstock, 1948)
Once the female produces her egg sacs she guards them until the spiderlings hatch. Once the spiderlings have hatched they leave the web (Milne, 1990).
Copulation amongis unique. A mature male spins a small “sperm web” and deposits a small quantity of semen on it. He then charges his palps with the sperm, abandons his habitat, and spends considerable effort to locate a female of his species. Once the female black widow spider has been located, courtship begins. The male vibrates the threads of the female’s snare to be sure she is the right species, for her to recognize him as a mate, and to make her receptive to mating. Mating takes place when the male inserts his papal organs into the spermathecal openings of the female. The spermatozoa are released onto the eggs. The eggs are laid onto a small web and are covered with more silk until they are completely surrounded by an egg sac or cocoon. This egg saw is then camouflaged, guarded, or carried by the female. Within the egg sac, the eggs hatch and spiderlings (juveniles) emerge. The female black widow spider’s egg sac is pear-shaped. In addition, the female can store a lifetime supply of sperm to fertilize all the eggs she will ever produce. (Hillyard, 1994; Snow, 1970; Kaston, 1953; Wallace et al, 1991; Foelix, 1996)
The female rarely leaves the web. She watches over the eggs in the egg sac until the spiderlings hatch. The spiderlings disperse soon after hatching, at which time parental care ceases and the spiderlings must fend for themselves.
Most spiders live for one year. Some are known to have lived 3 years in the wild, and in captivity, widow spiders may live for at least four years.
is timid, sedentary, solitary, cannibalistic, and nocturnal. The only social life it exhibits is when it mates. During the daylight hours, this spider spends its time in the silken tunnel of its web, which is the core of the snare. The female black widow spider hangs upside down in her web; her red hourglass marking is a visible warning signal. This spider will drop out of its web at the slightest disturbance and pretend that it is dead. The female black widow is usually clumsy when she is not in intimate contact with the lines of her snare. is a tangled web weaver. Its irregular, funnel-shaped web of coarse silk has a definite plan. Three structural levels can be recognized: an uppermost complex of supporting threads, a central zone of tangle threads, and a lower zone of vertical trap threads. Also, the black widow spider is greatly active in the autumn months and its web is spread over everything. In addition, most of these spiders live only a year, but the yearly population is divided into two faunas, one identified with spring and the second with fall. (Ferrand, 1988; Shuttlesworth, 1959; Preston-Mafham, 1996; Hillyard, 1994; Gertsch, 1979; Kaston, 1953)
is exclusively carnivorous and antagonistic. Ordinarily it feeds on insects; however, it also consumes wood lice, diplopods, chilopods and other arachnids. Usually, the black widow spider enswathes prey caught in its snare, bites it, and later drags it to its hub, or retreat, to be eaten. inflicts a small wound on its prey, uses its cheliceral teeth to mash it up, pours digestive enzymes on the prey; and sucks up the resulting food. The whole digestion process takes place outside the spider’s body. (Kaston, 1953; Snow, 1970; Preston-Mafham, 1996; Foelix, 1996; Levine and Miller, 1991; Gertsch, 1979)
A known predator is the mud-dauber wasp (Desert USA Magazine, 2004). The black widow spider spins a web which acts as a defense mechanism against predators. When a possible predator comes in contact with the web, it becomes entangled in the threads allowing the spider to wrap more silk around it and then inject it with its poison. Also, the female spider hangs upside down in her web so that her red hourglass mark serves as a warning signal to a predator (Farrand, 1988). (Desert USA Magazine, 2004; Farrand, 1988)
The black widow spider creates its own habitat wherever it spins its own web. With the aid of its web, the spider plays an active role in the ecosystem by helping to control insect populations.
Black widow spiders are fairly common and they are afforded no special conservation protections.
Matthew McCorkle (author), University of Michigan-Ann Arbor, Kerry Yurewicz (editor), University of Michigan-Ann Arbor.
living in the Nearctic biogeographic province, the northern part of the New World. This includes Greenland, the Canadian Arctic islands, and all of the North American as far south as the highlands of central Mexico.
living in the southern part of the New World. In other words, Central and South America.
living in landscapes dominated by human agriculture.
having coloration that serves a protective function for the animal, usually used to refer to animals with colors that warn predators of their toxicity. For example: animals with bright red or yellow coloration are often toxic or distasteful.
having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.
an animal that mainly eats meat
Found in coastal areas between 30 and 40 degrees latitude, in areas with a Mediterranean climate. Vegetation is dominated by stands of dense, spiny shrubs with tough (hard or waxy) evergreen leaves. May be maintained by periodic fire. In South America it includes the scrub ecotone between forest and paramo.
in deserts low (less than 30 cm per year) and unpredictable rainfall results in landscapes dominated by plants and animals adapted to aridity. Vegetation is typically sparse, though spectacular blooms may occur following rain. Deserts can be cold or warm and daily temperates typically fluctuate. In dune areas vegetation is also sparse and conditions are dry. This is because sand does not hold water well so little is available to plants. In dunes near seas and oceans this is compounded by the influence of salt in the air and soil. Salt limits the ability of plants to take up water through their roots.
a substance used for the diagnosis, cure, mitigation, treatment, or prevention of disease
animals which must use heat acquired from the environment and behavioral adaptations to regulate body temperature
parental care is carried out by females
union of egg and spermatozoan
forest biomes are dominated by trees, otherwise forest biomes can vary widely in amount of precipitation and seasonality.
having a body temperature that fluctuates with that of the immediate environment; having no mechanism or a poorly developed mechanism for regulating internal body temperature.
An animal that eats mainly insects or spiders.
fertilization takes place within the female's body
Having one mate at a time.
having the capacity to move from one place to another.
the area in which the animal is naturally found, the region in which it is endemic.
active during the night
rainforests, both temperate and tropical, are dominated by trees often forming a closed canopy with little light reaching the ground. Epiphytes and climbing plants are also abundant. Precipitation is typically not limiting, but may be somewhat seasonal.
breeding is confined to a particular season
reproduction that includes combining the genetic contribution of two individuals, a male and a female
mature spermatozoa are stored by females following copulation. Male sperm storage also occurs, as sperm are retained in the male epididymes (in mammals) for a period that can, in some cases, extend over several weeks or more, but here we use the term to refer only to sperm storage by females.
places a food item in a special place to be eaten later. Also called "hoarding"
living in residential areas on the outskirts of large cities or towns.
that region of the Earth between 23.5 degrees North and 60 degrees North (between the Tropic of Cancer and the Arctic Circle) and between 23.5 degrees South and 60 degrees South (between the Tropic of Capricorn and the Antarctic Circle).
Living on the ground.
defends an area within the home range, occupied by a single animals or group of animals of the same species and held through overt defense, display, or advertisement
the region of the earth that surrounds the equator, from 23.5 degrees north to 23.5 degrees south.
living in cities and large towns, landscapes dominated by human structures and activity.
an animal which has an organ capable of injecting a poisonous substance into a wound (for example, scorpions, jellyfish, and rattlesnakes).
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