Golden orb-web
spiders belong to the family Tetragnathidae,
subfamily Nephilinae. There are
two genera: Nephila (Golden orb-web spiders) and
the monophyletic genus Nephilengys
(hermit spiders). There are three species in the
genus Nephila: Nephila pilipes fenestrata
(black-legged golden orb-web spider), Nephila
senegalensis annulata (banded-legged golden
orb-web spider) and Nephila inaurata
madagascariensis (red-legged golden orb-web
spider).
The genus Nephilengys consists of a single
species, Nephilengys cruentata (white orb-web
spider). These large, obtrusive spiders are one
of the few spiders which can be identified down
to species without the aid of a microscope and a
fancy key. They are strictly web bound and
find walking on the ground cumbersome. Nephila
construct very large orb webs, often between
trees or bushes from 1.5m to 6m above the ground.
Their silk is golden in colour and
extremely strong. There are trip lines around the
web and quite often prey remains are strung
up to form a line through it’s center. Their
slightly angled webs are designed to catch large
flying insects and small birds are occasionally
snared, but rarely eaten. The female spider hangs
inverted in the center of the web, while one or
more males lurk on the periphery of the web.
Males are many times smaller than the females and
can be distinguished by their swollen
pedipalps which are similar to boxing gloves.
Nephila pilipes fenestrata has a creamy abdomen
with a blueish marbling towards the rear and
has tufts of hair on the first, second and fourth
legs. It is widely distributed throughout South
Africa, but absent from the drier western parts.
Nephila senegalensis annulata has black and
yellow abdominal markings with yellow bands on
its legs. It has the widest distribution
throughout South Africa. Nephila inaurata
madagascariensis is more or less black, silver
and
reddish-brown with red legs, and may be found in
northern KwaZulu/ Natal. Nephilengys
cruentata spins a characteristic white web with a
funnel-like retreat and is distributed
throughout the eastern coastal regions. It is
generally blacker than Nephila and has a rounder,
less cylindrical, abdomen with an orange/ red
breastplate.
Reproduction is similar for all Nephila. As in
the case of Nephila senegalensis annulata, the
male spins a small sperm web onto which he
deposits a drop of sperm which he sucks up into
his pedipalps. He will usually only approach the
female when she is otherwise occupied i.e.
feeding. He descends towards her and inserts his
pedipalps, one by one, into her genital
opening which is situated underneath her abdomen.
Copulation may take as long as 15 hours
and afterwards the now exhausted male retreats to
a safe place away from the female. When
ready to lay her eggs, she selects a suitable
site and constructs an egg sac using special
loopy
white silk. After a fortnight or so, the young
spiders hatch inside the eggsac. At this time
they
are still embryonic living off the yolk. Their
mouthparts, venom glands, digestive tracts and
spinning organs are underdeveloped, and only
after the yolk has been absorbed and their body
parts are properly developed do the spiderlings
cannibalise each other and must disperse. Their
life history follows a yearly cycle with the
females living slightly longer than the males.
These large, shy but beautiful spiders may look
formidable but are not aggressive, and even
those who walk into their webs are unlikely to be
bitten and although their bite is painful, it is
not of great medical importance.
|
