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Abdomen: The second of the two main parts of the
body of a spider. It is usually soft and easily damaged. |
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Araneomorph spiders: The more advanced spider
families, most of which can survive indefinitely in webs or other open
environments without suffering desiccation. Araneomorphs usually have only two booklungs on the underside of their abdomens. |
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Book lungs: Small pocket-like openings on the underside of the
abdomen. The advanced (araneomorph) spider
families have one of these on each side of the abdomen close to its front
end but primitive spiders (mygalomorphs) have
a second pair behind the first. |
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Calamistrum: A comb of stiff hairs on the second last segment of the fourth pair of legs, used to comb silk from the web-spinning
cribellum of some spiders. |
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Carapace: The relatively hard upper 'shell' of the front part of a spider. |
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Cephalothorax: The first of the two main parts of the body of a spider. This part has the chelicerae with fangs attached, the
pair of palps and the four pairs of legs
attached to it. |
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Chelicerae: A pair of short appendages at the front end of a spider. The
fangs are attached to the outer end of these structures, which often contain the spider's venom glands as well. The orientation of the pair of
fangs and the way they interact are of value for determining the family to which the spider belongs. Typically, mygalomorph fangs operate vertically
and in parallel whereas on araneomorphs they move transversely in a pincer action. |
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Claw tuft: A thick brush-like set of hairs at the end of the legs of
some spiders. This is located just behind the tarsal claws. |
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Compression bandage: An elastic bandage that is wrapped around a limb
over a bite site with sufficient tension to slow, but not stop, the flow
of blood through the site. |
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Cribellum: A flat plate-like structure projecting backwards from the underside of the female abdomen of some spiders and used as a
source of silk instead of one pair of spinnerets. In some families the silk-secreting part of this plate is divided into left
and right halves. |
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Diaxial fangs: A pair of fangs that operate in pincer fashion. This
arrangement is found on araneomorph spiders. |
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Egg sac: A container or wad of spider silk that may contain and protect several hundred eggs until they hatch. |
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Envenomation: Poisoning following the injection of a spider's venom into the skin. |
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Epigastric furrow: A groove across the underside of the abdomen that marks the rear edge of the book lungs and the point of entry into the
female genitalia. |
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Epigynum: The hardened, external mating structure found centrally on the underside of the abdomen of a female spider just in front of the
epigastric furrow. It is easily seen on fully mature araneomorphs but not on mygalomorphs or
immature araneomorphs. |
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Eye patterns: The set of four (or sometimes fewer) pairs of eyes found on the caput, which is the somewhat raised front upper end of the
cephalothorax just behind the fangs. These eyes are often arranged in two rows of four so we refer to the front ones as the anterior median and lateral
eyes (AME and ALE) and the rear ones as the posterior median and lateral eyes (PME and PLE). |
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Fangs: Tapering curved needles used by a spider to inject its venom into a victim. |
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Fovea: a short groove visible in the centre of the upper surface of the carapace. This may be straight or curved and may run lengthwise or
across the carapace. On some species it appears to be entirely missing. |
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Instar: An immature form of a spider. In general, instars have some resemblance to the adult female but they tend to have
different markings and their genitalia do not have a mature external appearance, if they are visible at all. |
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Moulting: When an immature spider breaks out of its body skin to grow larger. This is the only way spiders can increase in size as thy mature to
adulthood. Most spider species pass through several instar sizes before becoming adults and some long-lived mygalomorph females are said to moult
occasionally even after becoming adults. |
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Mygalomorph spiders: The more primitive spider families which usually die quickly from desiccation unless protected by a moist burrow. For this
reason they are mostly only active and outside the burrow at night and during rainy periods. |
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Necrotising arachnidism: Progressive ulceration and loss of skin around the site of a biting allegedly caused by a number of
araneomorph spider species. Note that there is only one Australian genus, Loxosceles, which is has been proven to
have this adverse effect on humans and it is very rare. The actual cause of the necrotizing phenomenon is uncertain and for this reason no fully effective
treatments for it are available in Australia at the present time.
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Neurotoxin: A nerve poison which is present in the venom of most spiders and is used to immobilise prey. Only a small number of spider
species have neurotoxins potent enough to be life-threatening to humans but most spiders have venom components that paralyse their normal prey, which typically
includes insects and other spiders.
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Palps: Also called pedipalps, these are short, leg-like structures attached to the front of the cephalothorax between the fangs and the first
pair of conventional legs. In females and in immature males they resemble small legs, although they have one less segment. In mature (or sometimes
nearly mature) males the terminal segments are modified into a bulb and needle that are used for mating. |
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Paraxial fangs: A pair of fangs that strike downwards in parallel arcs. This is the normal arrangement on a
mygalomorph spider. |
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Scopula: A dense brush-like mat hairs on the underside of the terminal segments of at least some legs on certain spider species.
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Sexual dimorphism: This term is used when the male and female of the same spider species have physical characteristics so different that they
appear to be different species. This is most obvious when the spiders are mature and it is often impossible to determine the sex of an immature spider
just by looking at its surface anatomy.
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Spinnerets: These are the web-spinning organs found on the underside of the abdomen at or near its rear end. There are at least two
pairs present and sometimes three but often one pair are notably larger than the others. The orientation of the set of spinnerets and the length and
pattern of silk-extruding spigots on each spinneret are sometimes important for identification purposes. |
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Spur: A sharp thorn-like projection from a segment of a leg. Spurs are much thicker and more tapering than the hairs found on the
legs of many spiders. |
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Tarsal bulb: The expanded end segment of the palps of a mature
male spider. This structure usually is shaped like a spherical bulb but has a hollow needle
(often coiled) projecting backwards from it. |
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Tarsal claws: A pair of small claws at the end of each leg, used by the spider to hold onto objects, including its own web.
Many species have a smaller median claw behind the main pair. |
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Tibia: The third segment of a spider's leg, counting inwards from the outer end of the leg. |
