THE STEINHART AQUARIUM - Gulf of Guinea Science ...

66 A Docent Field Guide to the Species of the Steinhart Aquarium
Remarks: Bright markings serve as warning to
predators. While eating a black widow may not
kill a bird or other small predator, the digestive
discomfort warns the attacker that this spider
is to be avoided. Males are less venomous and
also less brightly marked.
Black widow venom is highly potent (15 times
that of rattlesnakes and reportedly more potent
than that of cobras or coral snakes); however,
because the spider is not large, the chelicerae
cannot inject venom to depth or in quantity.
It is rare for bites to kill humans, though young
children or the elderly are likely to have severe
reactions. Most victims recover completely in
2–5 days.
Golden Orb Weaving Spider
Nephila sp. (Nephilidae)
Golden Orb Weavers
Distribution: Southeast U.S south through
Argentina and Peru. Nephilia spp. are found
worldwide in the tropics and subtropics.
Habitat: Areas of high humidity and relatively
open space; forest areas along trails and
clearing edges.
Appearance: Highly sexually dimorphic.
Females, which grow up to 8 cm, are 5–6 times
larger than males. Adults are mostly yellow
with elongated abdomen and long, hairy legs.
Diet: Small flying insects: beetles, flies, moths,
etc. After prey is entangled in the web, the
spider incapacitates it by biting and then
encases it in silk.
Reproduction: Mating is a tricky proposition
for orb weaving males. For successful
reproduction, males must successfully
stimulate females in order to prevent being
a meal for their would-be mate, though this
unfortunate ending is relatively rare with this
species.
Mortality/Longevity: Life span: a single season
(1 year).
Remarks: Orb weavers construct webs for
defense and capture of prey.
The silk of the web usually has a golden color
which is visible to the naked eye and is the
source of the common name.
The impressive web of most orb weavers is a
semi-permanent structure, repaired and rebuilt
daily as necessary.
This spider lives in hot places. The long
cylindrical abdomen of the spider may be
angled towards the sun to reduce the amount
of exposed body surface and thus prevent
overheating. The reflective silvery surface of
much of the body serves the same purpose.
See Nephila madagascariensis for more
information on Nephilia spp.
Madagascar Golden Orb Spider
Nephila madagascariensis (Nephilidae)
Golden Orb Weavers
Distribution: Various species of orb weaving
spiders are widely distributed. They exist in
the southern United States, Central and South
America, Southeast Asia, and the South Pacific.
Nephila madagascariensis is found on the island of
Madagascar and certain parts of Southern Africa.
Appearance: Females are much larger than
mature males, reaching 10–14 cm length when
full grown. Males are about one-sixth this size.
In females, the dorsal side of the abdomen has
bright yellow markings surrounded by a light
gray border. The rest of the body and legs are
black with patches of brown.
Diet: Eat insects that get caught in their webs,
primarily flying insects. They kill their prey with
a venomous bite. While painful, a bite from this
spider would not seriously hurt humans.
Reproduction and Development: Mating occurs
at the center of the web where the female lives. The
males stays in a corner of the web, and approaches
the female when she is eating or is in the process
of molting her exoskeleton, and mating occurs.
In about 30 days the eggs hatch. The nymph
spiderlings, each about as big as a pinhead remain
in the egg case for 5– 6 days until their first molt.
Then they emerge and stay in a tight cluster until
their second molt, about 24–30 days later. After
this molt, they begin to disperse.
Mortality/Longevity: Females usually live about
a year, and males about 6 mos.
Remarks: Golden orb spiders weave large,
strong webs out of golden colored silk. The
webs can be as big as 2 m across. The silk
strands are reputed to be five times stronger
than steel and three times more elastic than
Kevlar.
Spiders can produce up to seven types of
silk, each optimized for a certain task. These
can include silk for drag lines, structural silk,