mactans; she doesn't always live up to her
The largest member of the comb-footed spider
family, a female black widow averages about 1/2
inch in length; the male is considerably smaller.
It is shiny, coal black in color, and has long
slender legs and a round abdomen. The female is
almost always marked with a red hourglass-shaped
spot on her 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. The sides of the male's
abdomen is marked by four pairs of red and white
Young spiderlings are orange, brown, and
white. They acquire their black coloring with
Distribution and Habitat
Black widows are found throughout much of the
United States, from Massachusetts to Florida,
west to California, and throughout all four
deserts of the American Southwest. They are also
found in Canada, Mexico, the West Indies, and
The black widow spins a coarse irregularly
designed web which often has a short funnel of
silk. The male spins a similarly textured web but
much smaller. Cool dark places are chosen, in
cellars, outbuildings, ruined or abandoned
houses, under doorsteps and porches, beneath
floorboards or in piles of rubbish. In heavily
populated areas they are often found within city
dumps and littered areas. In desert regions they
can be found in almost any crevice in the soil,
as well as in cacti and agave plants.
When adult, the male spins a very tiny web,
upon which he deposits seminal fluid. He then
charges his pedipalps with the sperm, abandons
his home, and goes off in search of a mate. Once
he has located a female black widow the male
vibrates the threads of the female's web to make
sure she is of the right species, and for her to
recognize him as a mate. In mating the male
simply transfers the sperm from the reservoir in
his pedipalps to the female's body. One mating is
sufficient for several bouts of egg-laying, since
the female stores the sperm and uses it over a
period, often of months.
The eggs are laid in silken cocoons, which are
guarded by the female guards until the
spiderlings hatch. Once hatched, however, the
spiderlings leave the web and fend for
Black widows feed primarily on insects, but
will also take other arachnids. Most prey is
encased in silk upon being trapped in the web.
Once secured, the prey is paralyzed by the black
widow's venom. Saliva left behind by the spider's
bite starts digesting the prey almost
immediately, and within an hour or two the spider
is able to feed.
Habits and Behaviors
Black widows are timid, sedentary, solitary,
cannibalistic, and nocturnal.
The only time more than one black widow will
be found together is during mating and just prior
to newly-hatched spiderlings leaving their
The black widow spins a web which acts as a
defense mechanism against predators. When a
potential predator comes in contact with the web,
it becomes entangled in the threads allowing the
spider to wrap silk around it and then inject it
A female black widow usually hangs upside down
in her web so that her red hourglass mark serves
as a warning signal to a predator.
This spider will usually drop out of its web
at the slightest disturbance and feign death.
The bite of a black widow is distinguished by
a double puncture wound. Black widow venom is a
neurotoxin, meaning that it blocks the
transmission of nerve impulses. A bitten human
usually suffers from a painful rigidity in the
area around the bite, but if treated properly and
promptly the bite is rarely fatal.
Despite its common name, a female black widow
does not invariably eat the male after mating. In
fact, it is actually fairly common for the male
to live long enough to mate with several females.
It is possible, however, that after several
matings the male may become enfeebled enough to
become entangled in a female's web, upon which
time the female would act in the same way she
would if any other type of prey found itself
caught in her web.
family Theridiidae (cobweb spiders)
genus & species Latrodectus mactans
Animal Diversity Web http://animaldiversity.org/accounts/Latrodectus_mactans/
Questions or comments about