The Find-a-Spider Guide

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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. It is usually soft and easily damaged.

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. Araneomorphs usually have only two booklungs on the underside of their abdomens.

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 relatively 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 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.

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-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.

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 may contain and protect several hundred eggs until they hatch.

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 that marks the rear edge of the book lungs and the point of entry into the female genitalia.

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 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).

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. On some species it appears to be entirely missing.

Click to enlarge 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.

Click to enlarge 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.

Click to enlarge 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.

Click to enlarge 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.

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 but most spiders have venom components that paralyse their normal prey, which typically includes insects and other spiders.

Click to enlarge 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.

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-like mat hairs on the underside of the terminal segments of at least some legs on certain spider species.

Click to enlarge 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.

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 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.

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 many spiders.

Click to enlarge 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.

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.

Email Ron Atkinson for more information.    Last updated 21 April 2015.