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Glossary of Terms

NOTE: To see each illustration more clearly click on it to produce an enlarged version

Click to enlarge Abdomen: The second of the two main parts of the body of a spider.

Click to enlarge Araneomorph spiders: The more advanced spider families, most of which can survive indefinitely in webs or other open environments without suffering desiccation.

Click to enlarge 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.

Click to enlarge 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.

Click to enlarge Carapace: The hard upper 'shell' of the front part of a spider.

Click to enlarge 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.

Click to enlarge Chelicerae: A pair of short appendages at the front end of a spider. The fangs are attached to these structures, which often contain the spider's venom glands as well.

Click to enlarge 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.

Click to enlarge 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.

Click to enlarge Cribellum: A flat plate projecting backwards from the underside of the female abdomen of some spiders, 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.

Click to enlarge Diaxial fangs: A pair of fangs that operate in pincer fashion. This arrangement is found on araneomorph spiders.

Click to enlarge Egg sac: A container or wad of spider silk that encloses up to 300 eggs until hatching occurs.

Click to enlarge Envenomation: Poisoning following the injection of a spider's venom into the skin.

Click to enlarge Epigastric furrow: A groove across the underside of the abdomen near its front end.

Click to enlarge 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.

Click to enlarge Eye patterns: The set of eight (or sometimes only six) eyes found on the caput, which is the somewhat raised front upper end of the cephalothorax, just behind the fangs. There are often two rows of four eyes so we refer to the anterior (front row) median and lateral eyes and the posterior (second row) median and lateral eyes.

Click to enlarge Fangs: Tapering curved needles used by a spider to inject its venom into a victim.
Click to enlarge 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.

Click to enlarge Instar: An immature form of a spider. Most spider species pass through at least five instar sizes before becoming adults. This is the only way they can grow. In general, instars have some resemblance to the adult female but they lack mature surface genitalia and often also have different markings.

Click to enlarge Moulting: When an immature spider breaks out of its hard body shell to grow larger. This occurs at least five times before the spider reaches adulthood.

Click to enlarge Mygalomorph spiders: The more primitive spider families which usually die quickly unless protected by a moist burrow. For this reason they are mostly only active at night and during rainy periods.

Click to enlarge Necrotising arachnidism: Progressive ulceration and loss of skin around the site of a biting by a number of araneomorph spider species. Its cause is uncertain and for this reason no fully effective treatments are available at the present time.

Click to enlarge 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.

Click to enlarge Palps: 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.

Click to enlarge Paraxial fangs: A pair of fangs that strike downwards in parallel arcs. This is the normal arrangement on a mygalomorph spider.

Click to enlarge Scopula: A dense brush of hairs on the underside of the terminal segments of the legs of some spiders.

Click to enlarge Sexual dimorphism: When the male and female of the same spider species have physical characteristics so different that they appear not to be the same species. This is most obvious when the spiders are mature.

Click to enlarge 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.

Click to enlarge 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 most spiders.

Click to enlarge Tarsal bulb: The expanded end segment of the palps of a mature male spider. This structure usually is like a bulb but has a hollow needle (sometimes coiled) projecting backwards from it.

Click to enlarge 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.

Click to enlarge Tibia: The third segment of a spider's leg, counting inwards from the outer end of the leg.

Ron Atkinson for more information.    Last updated 17 April 2009.