Spider

Araneaespidersegg sacspider venomsspiderlingarachnidsaraneidegg sacsspider Arachnidic
Spiders (order Araneae) are air-breathing arthropods that have eight legs and chelicerae with fangs able to inject venom.wikipedia
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Arachnid

Arachnidaarachnidsarachnoid
They are the largest order of arachnids and rank seventh in total species diversity among all orders of organisms.
Spiders are the largest order in the class, which also includes scorpions, ticks, mites, harvestmen, and solifuges.

Spider anatomy

pedicelgenitaliaabdomen
Anatomically, spiders differ from other arthropods in that the usual body segments are fused into two tagmata, the cephalothorax and abdomen, and joined by a small, cylindrical pedicel. In spiders, the cephalothorax and abdomen are joined by a small, cylindrical pedicel, which enables the abdomen to move independently when producing silk.
The anatomy of spiders includes many characteristics shared with other arachnids.

Mesothelae

mesothelemesotheles
In all except the most primitive group, the Mesothelae, spiders have the most centralized nervous systems of all arthropods, as all their ganglia are fused into one mass in the cephalothorax. It shows no sign of segmentation, except that the primitive Mesothelae, whose living members are the Liphistiidae, have segmented plates on the upper surface.
The Mesothelae are a suborder of spiders (order Araneae) that includes a single living (extant) family, Liphistiidae, and a number of extinct families.

Orb-weaver spider

Araneidaeorb-weaver spidersorb weaver
It now appears that the spiral orb web may be one of the earliest forms, and spiders that produce tangled cobwebs are more abundant and diverse than orb-web spiders.
Orb-weaver spiders or araneids are members of the spider family Araneidae.

Spider silk

silkgossamersilken
Their abdomens bear appendages that have been modified into spinnerets that extrude silk from up to six types of glands.
Spider silk is a protein fibre spun by spiders.

Spider web

webcobwebwebs
Spider webs vary widely in size, shape and the amount of sticky thread used.
A spider web, spiderweb, spider's web, or cobweb (from the archaic word coppe, meaning "spider") is a structure created by a spider out of proteinaceous spider silk extruded from its spinnerets, generally meant to catch its prey.

Arthropod

ArthropodaarthropodsEuarthropoda
Spiders (order Araneae) are air-breathing arthropods that have eight legs and chelicerae with fangs able to inject venom. Spiders are chelicerates and therefore arthropods.
Their vision relies on various combinations of compound eyes and pigment-pit ocelli: in most species the ocelli can only detect the direction from which light is coming, and the compound eyes are the main source of information, but the main eyes of spiders are ocelli that can form images and, in a few cases, can swivel to track prey.

Arachnophobia

arachnophobicarachnophobefear of spiders
An abnormal fear of spiders is called arachnophobia.
Arachnophobia is the unreasonable fear of spiders and other arachnids such as scorpions.

Chelicerata

cheliceratecheliceratesCheliceriformes
Spiders are chelicerates and therefore arthropods.
It contains the sea spiders, arachnids (including scorpions, spiders, and potentially horseshoe crabs ), and several extinct lineages, such as the eurypterids.

Insect

Insectainsectsbugs
Unlike insects, spiders do not have antennae.
Other terrestrial arthropods, such as centipedes, millipedes, scorpions, and spiders, are sometimes confused with insects since their body plans can appear similar, sharing (as do all arthropods) a jointed exoskeleton.

Venom

venomousvenomsvenomous animals
Spiders (order Araneae) are air-breathing arthropods that have eight legs and chelicerae with fangs able to inject venom. Spiders' chelicerae have two sections and terminate in fangs that are generally venomous, and fold away behind the upper sections while not in use.
Venomous arthropods include spiders, which use fangs — part of their chelicerae — to inject venom; and centipedes, which use forcipules — modified legs — to deliver venom; along with scorpions and stinging insects, which inject venom with a sting.

Pedipalp

palppedipalpspalpi
They also grind food with the bases of their pedipalps, as arachnids do not have the mandibles that crustaceans and insects have.
Pedipalps (commonly shortened to palps or palpi) are the second pair of appendages of chelicerates – a group of arthropods including spiders, scorpions, horseshoe crabs, and sea spiders.

Spinneret

spinneretsglandsspigots
Their abdomens bear appendages that have been modified into spinnerets that extrude silk from up to six types of glands.
A spinneret is a silk-spinning organ of a spider or the larva of an insect.

Mygalomorphae

mygalomorphmygalomorph spidersmygalomorph spider
The main groups of modern spiders, Mygalomorphae and Araneomorphae, first appeared in the Triassic period, before.
The Mygalomorphae or mygalomorphs are an infraorder of spiders.

Silk

silk weavingsilk industrysilken
In spiders, the cephalothorax and abdomen are joined by a small, cylindrical pedicel, which enables the abdomen to move independently when producing silk.
Other types of arthropods produce silk, most notably various arachnids, such as spiders.

Bagheera kiplingi

The species Bagheera kiplingi was described as herbivorous in 2008, but all other known species are predators, mostly preying on insects and on other spiders, although a few large species also take birds and lizards.
No other known species of omnivorous spider has such a markedly herbivorous diet.

Lampshade spider

Hypochilidaelampshade spidersHypochiloidea
This is also the case for some basal araneomorph spiders, like the family Hypochilidae, but the remaining members of this group have just the anterior pair of book lungs intact while the posterior pair of breathing organs are partly or fully modified into tracheae, through which oxygen is diffused into the haemolymph or directly to the tissue and organs.
Lampshade spiders, family Hypochilidae, are among the most primitive of araneomorph spiders.

Book lung

book lungsbook gillbook gills
The blood of many spiders that have book lungs contains the respiratory pigment hemocyanin to make oxygen transport more efficient.
A book lung is a type of respiration organ used for atmospheric gas exchange that is found in many arachnids, such as scorpions and spiders.

Araneomorphae

araneomorpharaneomorphs araneomorph
The main groups of modern spiders, Mygalomorphae and Araneomorphae, first appeared in the Triassic period, before. This is also the case for some basal araneomorph spiders, like the family Hypochilidae, but the remaining members of this group have just the anterior pair of book lungs intact while the posterior pair of breathing organs are partly or fully modified into tracheae, through which oxygen is diffused into the haemolymph or directly to the tissue and organs.
The Araneomorphae (also called the Labidognatha) are an infraorder of spiders.

Uloboridae

cribellate orb-weaversuloboridcribellate orb weavers
The families Uloboridae and Holarchaeidae, and some Liphistiidae spiders, have lost their venom glands, and kill their prey with silk instead.
Uloboridae is a family of nonvenomous spiders, known as cribellate orb weavers or hackled orb weavers.

Liphistiidae

liphistius trapdoor spider
The families Uloboridae and Holarchaeidae, and some Liphistiidae spiders, have lost their venom glands, and kill their prey with silk instead. It shows no sign of segmentation, except that the primitive Mesothelae, whose living members are the Liphistiidae, have segmented plates on the upper surface.
They are among the most basal living spiders, belonging to the suborder Mesothelae.

List of six-eyed spiders

six-eyed spidersix eyessix-eyed spiders
Of these, those with six eyes (such as Periegops suterii) are the most numerous and are missing a pair of eyes on the anterior median line; other species have four eyes and some just two.
Six-eyed spiders are spiders that, unlike most spider species miss the principal pair of eyes, leaving them with only six eyes instead of the usual eight.

Chelicerae

cheliceracheliceralcheliceral fang
Spiders (order Araneae) are air-breathing arthropods that have eight legs and chelicerae with fangs able to inject venom.
Commonly referred to as "jaws", some chelicerae, such as those found in spiders, are hollow and contain (or are connected to) venom glands, and are used to inject venom into prey or a (perceived) threat.

Fang

fangsBitefang-like
Spiders' chelicerae have two sections and terminate in fangs that are generally venomous, and fold away behind the upper sections while not in use.
Spiders also have external fangs, which are part of the chelicerae.

Tagma (biology)

tagmatatagmaparts
Anatomically, spiders differ from other arthropods in that the usual body segments are fused into two tagmata, the cephalothorax and abdomen, and joined by a small, cylindrical pedicel.
For example, the one-time terms "cephalothorax" and "abdomen" of the Araneae, though not yet strictly regarded as invalid, are giving way to prosoma and opisthosoma.