Nephilidae (Golden Orb-Web Spiders)
by Frikkie Loots
General Information about Nephilidae
The spider family Nephilidae
is large, with 75 described species in four genera. They were firstly grouped
in the families Araneidae and Tetragnathidae. The genus Singafrotypa was moved
to Araneidae in 2002.
The generic name Nephila is derived from Greek,
"nen" meaning "to spin" and "philos" meaning
"love" thus meaning "fond of spinning". In South Africa, we have 3 genera represented by 6 different species.
Mating and
reproduction
Nephilidae have great sexual dimporphism. The pedipalps have
evolved into enlarged, complex palps which break off inside of the
females' copulatory openings after copulation.
The broken palps
serve as mating plugs, which makes future matings with a mated female more
difficult. This genera of
spiders also participate in mate-guarding; a mated male will stand guard by his
female and chase off other males, thereby increasing the mated male's paternity
share. Mated males are castrated in the process of mate plugging, though this
may be an advantage in mate guarding, as mated males have been observed to
fight more aggressively and win more frequently than virgin males.
So while the
female spiders are still polyandrous, the males have become monogamous.The female Nephila
constructs her egg sac on a leaf or tree bark; and produce about 400 - 1500 eggs
per sac.
Prey capture
A large vertical, sulfurous yellow orb-web is constructed, which has the top section missing in
adult webs.
Juvenile spiders
construct complete orb webs. In semi-social populations, their webs are joined
together forming an awesome, almost impenetrable curtain of webs. These webs
are supported by anchor strings of silk in front and behind the orb-web.
The web is usually
supported between two trees, buildings, fences and can span enormous spaces,
with the orb up to a meter wide, about 1.5 meters or more from the ground and
is capable of capturing small birds. There is no evidence that these birds are
eaten but they may be cut out of the web by the spider.
Unlike most orb-webs,
nephilid webs are partially repaired and not replaced. Most of the activity is
conducted by day (diurnal).
The obvious colour of
the main strands are believed to act as a "house hold insurance policy“ to the
spider by advertising it's presence to large creatures such as birds, so that
they don't damage it by flying through.
Building such
elaborate webs is energy expensive and preventing large scale damage to the web
is important.Some theories suggest
that the UV properties of the silk attract insects in the same way that the UV
pathways leading to the nectar in flowers do.
Commensal species
There are often one
or more tiny spiders with silver triangular abdomens on Nephila webs. These are called
dewdrop spiders of the genus Argyrodes (family Theridiidae) and they clean the
orb-webs of prey too small for the host spider.
The South African Orb-web species:
Nephila komazi (Giant Nephila)
The largest of the Nephiladae was believed to be extinct until in 2009 it was re
discovered in the Zululand area and now can also be found in Madagascar.
Largest of the Golden Orb web spiders with a leg span measuring at 120mm
(12cm). Its carapace is silvery, Abdomen is long and cylindrical extending
beyond its spinnerets. It has a bold black and pale yellow pattern on its
carapace which is one of the key ways to identify this spider.
Legs are black
with little brushes of hair on them. This spider is so large in fact that it’s
been known to catch birds! Their large Orb webs are built between trees with
the female sitting in the middle and the not so much smaller males (which is
rare in the Nephila family as usually the males are substantially smaller than
the females) sitting on the edges of the web.
Nephila fenestrata (Black-legged Nephila)
One of the more
common spiders of the Nephila family that we can see here in KZN as they love
forested areas, usually between January to July (but if conditions are right
they will stay till the end of August).
Easiest way to identify this spider is
by its black, very hairy legs. Carapace is oval in shape and has white and
black patterns with often a few yellow spots. The Black-legged Nephila’s like
to make their nests either in the open or amongst trees, but they also seem to
enjoy making their webs near human habitations which often causes problems as
many people don’t enjoy waking up to a spider that has a leg span of about
100mm (10cm).
The females generally sits in the middle of the web and the much
smaller males sit around the edges of the web.
Nephilengys cruentata (Hermit Spider)
The hermit spider is
quite a beautiful spider. For a spider it can grow to be rather large. These
particular spiders like to build a funnel shaped web where they can hide from
view and be safe during resting times and times of stress.
Attached to that
funnel shape is a normal spider web that is used for catching prey. These are
quite secretive spiders and do not like to be out in the open and that is why
the spend most of their time in the safety of their funnel.
They have a beautiful
coloration which in nature almost always means danger. Their legs are red,
yellow and black and their abdomen is black with white spots. As with all
spiders the female is bigger than the males.
This spider in
particular normally can be found with many of the same species in close
proximity. They are also commonly found near and around human dwellings.
Clitaetra irenae- Tree Nephila
This Spider is quite
hard to find as its colouration is perfect for blending in with its
surroundings (normally tree bark), and you do need to know what it looks like
and where to look.
It is called the Tree nephila as it lives on the tree bark
where it constructs a permanent web. Its colouration is mostly a pale brown
with some spots of red and black.
This spider occurs in
the coastal plain forests of Maputaland in KwaZulu-Natal South Africa. It loves
very close or dense canopy.
Nephila senegalensis (Banded-legged Nephila)
A beautiful spider
that has a very interesting and distinguishing pattern on its legs. It has two
yellow streaks on its front legs which gained it its name banded-legged
nephila. Being a Nephila it is a large spider and can be viewed near Oom Pine’s
house in the forest.
Nephila inaurata (Red-legged Nephila)
The legs on this
species are red and almost see through. They are large spiders and like to make
webs near and around human settlements and buildings. They have a small abdomen
for their size and quite long legs.
