|
The Black Widow— Latrodectus
mactans
DESCRIPTION
Adult -- Like all spiders, the black widow has 8 legs;
however, males and females differ in appearance. Females
are about 40 mm long with legs outstretched and have
black, globular abdomens about 9 by 13 mm marked with
a red or yellow hourglass shape underneath. Males are
lighter in color and have a red or pale brown stripe
down the middle of their backs from which white or yellow
streaks radiate. Males are smaller (up to 30 mm long
with legs outstretched). The male pedipalps (biting
appendages at front of head) are noticeably swollen.
Egg -- Eggs are incorporated into grayish, silken balls
about 12 to 15 mm in diameter. These egg masses contain
200 to 900 eggs and are found in the spider's web.
Nymph -- Entirely white at first, nymphs develop through
five to eight instars. As they develop, nymphs become
more similar in appearance to adult males, though smaller.
--------------------------------------------------------------------------------
BIOLOGY
Distribution -- Though more abundant in the southern
states, the black widow spider occurs throughout most
of the Western Hemisphere. This species may hide in
sheltered, dimly lit places such as barns, garages,
basements, outdoor toilets, hollow stumps, rodent holes,
trash, brush, and dense vegetation. Black widows usually
seek dry, sheltered sites such as buildings during periods
of cold weather.
Feeding Habits -- This spider feeds primarily on insects
and other arthropods but, when disturbed, it may bite
people or animals.
Damage -- The female black widow possesses a venom
15 times more potent than rattlesnake venom. The bite
is like a pin prick but causes pain within a few minutes
of the attack. The pain spreads rapidly to arms, legs,
chest, back, and abdomen. Chills, vomiting, difficult
respiration, profuse perspiration, delirium, partial
paralysis, violent abdominal cramps and spasms may occur
within a few hours of the bite. The victim usually recovers
in 2 to 5 days; about 5% of all black widow attacks
are fatal. The black widow, however, usually bites people
only when its web is disturbed. Male black widows do
not bite.
Life History -- The black widow spider overwinters
as a young adult in buildings or in sheltered places
outdoors. In late spring, after a prolonged courtship,
mating occurs. Soon afterward the female kills her mate
and begins laying eggs. The grayish silken ball of eggs
is attached to an irregular, tangled web with a funnel-shaped
exit. Each female constructs 5 to 15 egg balls, each
of which contains 200 to 900 eggs.
Young spiders emerge from the ball in 10 to 30 days.
They are cannibalistic at this stage. Only a few nymphs
from each egg mass survive. They require 2 to 3 months
to develop into adults. Older adults die the same summer
or autumn after laying eggs. The new generation of adults
survives through the winter.
|
