Arthropoda , Arachnida , Araneida , Araceida , is a generic term for all species of the order Araneida or Araneae. It is found worldwide except Antarctica. From sea level to 5,000 meters above sea level, it is terrestrial.
White-fronted tall spider
Spider body lengths range from 0.05 mm to 60 mm. The body is divided into head, chest and abdomen. Some species have breastplates on the back of the cephalothorax (some do not), and the front of the cephalothorax usually has 8 single eyes (there are also 6, 4, 2, 0), arranged in 2 to 4 rows. There is a large thoracic plate on the ventral surface, and the lower lip is between the two frontal lobes in front of the thoracic plate. The abdomen is not segmented, and the ventral stalk evolves from the 1st abdominal segment (7th body segment). The abdomen is mostly round or oval, and some have various protrusions and strange shapes. The ventral surface spindler evolved from the appendages, a few primitive species had 8, slightly in the front position; most species had 6 spinners, located in front of the anus at the rear end of the body; and some species had 4 spinners, and there were many spinning tubes on the spindle, connected with various silk glands, and the spindles were spun out of the yarn. The sensory organs are the eye, various sensory hairs, auditory hairs, organ-shaped organs, and tarsal organs.
spider
Spiders are surrounded by chitinoskeletal exoskeletons, and the body is clearly divided into cephalothorax and abdomen, often connected by a thin stalk that the first abdominal segment of the abdomen becomes, without a tail node or tail whip. Spiders have no compound eyes, the cephalothorax has 6 pairs of appendages, the first and second pairs belong to the head appendages, of which the first pair is mostly 2 segments of the claws, most of the basal bulges are claws, the tips and fine parts of the end are claws, the teeth are tubular, and the poisonous glands in the cetia or cephalothorax are derived from this. The second pair of appendages is called foot whiskers, shaped like a foot foot, but only 6 segments, the basal segment forms a jaw-like protrusion near the mouth, which can assist feeding, the female spider terminal has no major changes, and the male spider foot whisker segment is specialized as a reproductive auxiliary organ, with sperm storage, sperm transmission structure, called limb tentacles. The third to sixth pairs of appendages are foot walking, consisting of 7 segments, with claws at the end and a clump of hard hairs under the claws, so they are suitable for crawling on smooth objects.
Most spiders have venom glands, claws and claws have two types of movements, burrowing spiders are mostly up and down, and spiders that hunt on the ground and have webs in the air are swept like pincers.
No antennae, no wings, no compound eyes, only one eye, generally there are 8 eyes, but there are also 6, 4, 2 eyes, some genera even have no eyes, in terms of the color and function of the eyes, and there are two kinds of night and day.
The mouth organs of spiders are composed of the jaw leaves of the claws, tentacles and stems, the upper lip and the lower lip, which have the functions of poisoning, catching, crushing food, and sucking juice.
Some spiders have tufts of hairs made up of sticky hairs under their tarsal claws, which have the ability to crawl on vertical, smooth objects. Web-knotted spiders have several claw-like spines near the tip of the tarsal joint, called secondary claws.
Most spiders do not have knots in their abdomen. The presence or absence of an exotropic organ (called a reproductive triumvirus) is an important feature in the identification of female species. In the middle of the ventral surface of the abdomen or the rear end of the ventral surface has a special spinning apparatus, three pairs of spinning instruments according to their position, called the front, middle and rear spinners, the top of the spinning apparatus has a membranous spinning tube, surrounded by hairs, the number of spinning tubes of different spiders is different, different shapes of spinning tubes, spinning different spider silk, spinning tube sieves, but also spinning organs, like the sieve of the rhinoceropod family Offidae, there are 9600 spindles on the sieve, which can be seen that the silk it spins is extremely delicate. There are 8 kinds of silk glands that are introduced outside the body through the spinning tube, and the size and number of silk glands increase with the growth and successive molting of spiders. Spider silk is a bone protein that is very sticky, tough and elastic, and hardens when it is spit out in the air.
Hermaphroditic, the male is smaller than the female, the metatarsal segment of the male tentacle develops into a tentacle, and the female has an exoviraptor after the last molt.
There are 3 pairs of foot steps, divided into basal segments, turning nodes, leg segments, knee segments, tibia segments, posterior tarsal segments, tarsal segments, and tarsal segments (with claws on the upper body). The foot is covered with bristles and has several sensory organs, such as elongated cup hairs (which feel airflow and vibration). After the foot is cut, it can be regenerated the next time it molts. 8 or less in one eye. Some foot and palate muscles attach to the intrathracic bone of the cephalothorax. There is a slender ventral stalk connecting the cephalot to the abdomen. Due to the presence of the ventral stalk, the abdomen can swing freely when spinning. The nervous system is completely concentrated on the cephalothorax, with a brain (suprapharyngeal ganglia) on the pharynx and a subesophageal ganglia. Fissures of sensory organs are scattered throughout the body or near the joints of the foot and are used for vibration or hearing.
The abdomen is not segmented and has a digestive system, heart, reproductive organs and silk glands. When eating, the digestive juice is first spit out, digested outside the body, and then inhaled the liquefied food. It has both a biblical lung and a trachea, but the orthopedic suborder has only a bibliary lung, and the zygomatic palate has only a trachea. With the exception of the arachnidae , there are venom glands located within or under the dorsal carapace , and the venom ducts are opened near the end of the crayon through the crayon , and the venom glands may have originated as a supplementary digestive gland. The venom secretions of many species of spiders are all digestive enzymes, and some can subdue predators and even fight against predators (including vertebrates).
The venom of widow spiders of the genus Latrodectus, especially the black widow (L. mactans), is nerve-tinged and painful. Black widows are often suspended upside down on a web , with a black body and a red hourglass-shaped stripe on the abdomen , often with a red stripe. Bites of the brown hermit spider (Loxosceles reclusa) cause local necrosis. The chemical composition of spider silk is similar to that of insect silk, which is a silk heart protein. The silk glands may come from excretory organs and there are 6 types. Various types of silk glands produce different types of silk, the filaments produced by the vesicular glands are used to bind the prey, the pot-bellied glands produce sticky globules that spiral into the spider web, the silk of the round granular glands constitute the egg sacs, and the silk of the silk glands on the stomach of the male spider is discharged from the spit duct between the abdomen and lungs and covers the surface of the sperm droplets. The original Mesothelae family had only 2 species of silk glands, but there were 6 species of round spiders. Spindles are metamorphic appendages, 1 to 4 pairs (two pairs each for the 10th and 11th abdominal segments), most of which have 3 pairs, while the middle pair in the front row disappears, or degenerates into a non-functional tongue or flat sieve, with thousands of spit wire openings.
According to literature, there are 42,055 species of spiders in 3,821 genera known worldwide (2010), and about 3,800 species are recorded in China, belonging to 67 families. There are 14 orders in the spider order, 5 orders have been extinct, and 7 orders have been found in China.
This article is edited by headline encyclopedia users Wanding Xingchen Feifei and Shan Chuan.