Spider in the context of Female anatomy

Terrestrial animals are animals that live predominantly or entirely on land (e.g., cats, chickens, ants, most spiders), as compared with aquatic animals (e.g., fish, whales, octopuses, lobsters, etc.), who live predominantly or entirely in bodies of water; and semiaquatic animals (e.g., crocodilians, seals, platypus and most amphibians), who inhabit coastal, riparian or wetland areas and rely on both aquatic and terrestrial habitats. While most insects (who constitute over half of all known species in the animal kingdom) are terrestrial, some groups, such as mosquitoes and dragonflies, spend their egg and larval stages in water but emerge as fully terrestrial adults (imagos) after completing metamorphosis.

Terrestrial animals conduct respiratory gas exchange directly with the atmosphere, typically via specialized respiratory organs known as lungs, or via cutaneous respiration across the skin. They have also evolved homeostatic features such as impermeable cuticles that can restrict fluid loss, temperature fluctuations and infection, and an excretory system that can filter out nitrogenous waste in the form of urea or uric acid, in contrast to the ammonia-based excretion of aquatic animals. Without the buoyancy of an aqueous environment to support their weight, they have evolved robust skeletons that can hold up their body shape, as well as powerful appendages known as legs or limbs to facilitate terrestrial locomotion, although some perform limbless locomotion using body surface projections such as scales and setae. Some terrestrial animals even have wings or membranes that act as airfoils to generate lift, allowing them to fly and/or glide as airborne animals.

Silk is a natural protein fiber, some forms of which can be woven into textiles. The protein fiber of silk is composed mainly of fibroin. It is most commonly produced by certain insect larvae to form cocoons. The best-known silk is obtained from the cocoons of the larvae of the mulberry silkworm Bombyx mori, which are reared in captivity (sericulture). The shimmery appearance of silk is due to the triangular prism-like structure of the silk fiber, which causes silk cloth to refract incoming light at different angles, thus producing different colors.

Harvested silk is produced by numerous insects; generally, only the silk of various moth caterpillars has been used for textile manufacturing. Research into other types of silk, which differ at the molecular level, has been conducted. Silk is produced primarily by the larvae of insects undergoing complete metamorphosis, but some insects, such as webspinners and raspy crickets, produce silk throughout their lives. Silk production also occurs in hymenoptera (bees, wasps, and ants), silverfish, caddisflies, mayflies, thrips, leafhoppers, beetles, lacewings, fleas, flies, and midges. Other types of arthropods also produce silk, most notably various arachnids, such as spiders.

A gill (/ɡɪl/ ) is a specialized respiratory organ that many aquatic animals use for aquatic gas exchange, i.e. to extract dissolved oxygen from water and to excrete carbon dioxide. Branchia (pl.: branchiae, from Ancient Greek βράγχια) is the zoologists' academic name for gills.

The gills of some semi-aquatic clades (e.g. crabs, terrestrial hermit crabs and amphibious fishes), have also adapted to allow air respiration (breathing) on land provided the gills are kept moist. In some terrestrial chelicerates species (tetrapulmonates such as spiders and scorpions), their ancestral gills have evolved into fully air-breathing book lungs. In some planktivorous bony fish species (e.g. silver and bighead carps), the gills are also used as a filter feeding organ via comb-like projections called gill rakers.

In biology, being semiaquatic refers to various macro-organisms that live regularly in both aquatic and terrestrial environments. When referring to animals, the term describes those that actively spend part of their daily time in water (in which case they can also be called amphibious), or land animals that have spent at least one life stage (e.g. as eggs or larvae) in aquatic environments. When referring to plants, the term describes land plants whose roots have adapted well to tolerate regular, prolonged submersion in water, as well as emergent and (occasionally) floating-leaved aquatic plants that are only partially immersed in water.

Examples of semiaquatic animals and plants are given below.

The subphylum Chelicerata (from Neo-Latin, from French chélicère, from Ancient Greek χηλή (khēlḗ) 'claw, chela' and κέρας (kéras) 'horn') constitutes one of the major subdivisions of the phylum Arthropoda. Chelicerates include the sea spiders, horseshoe crabs, and arachnids (including harvestmen, scorpions, spiders, solifuges, ticks, and mites, among many others), as well as a number of extinct lineages, such as the eurypterids (sea scorpions) and chasmataspidids.

Chelicerata split from Mandibulata by the mid-Cambrian, as evidenced by stem-group chelicerates like Habeliida and Mollisonia present by this time. The surviving marine species include the four species of xiphosurans (horseshoe crabs), and possibly the 1,300 species of pycnogonids (sea spiders), if the latter are indeed chelicerates. On the other hand, there are over 77,000 well-identified species of air-breathing chelicerates, and there may be about 500,000 unidentified species.

Arachnids are arthropods in the class Arachnida (/əˈræknɪdə/) of the subphylum Chelicerata. Arachnida includes, among others, spiders, scorpions, ticks, mites, pseudoscorpions, harvestmen, camel spiders, whip spiders and vinegaroons.

Adult arachnids have eight legs attached to the cephalothorax. In some species the frontmost pair of legs has converted to a sensory function, while in others, different appendages can grow large enough to take on the appearance of extra pairs of legs.

Insecticides are pesticides used to kill insects. They include ovicides and larvicides used against insect eggs and larvae, respectively. The major use of insecticides is in agriculture, but they are also used in home and garden settings, industrial buildings, for vector control, and control of insect parasites of animals and humans.

Acaricides, which kill mites and ticks, are not strictly insecticides, but are usually classified together with insecticides. Some insecticides (including common bug sprays) are effective against other non-insect arthropods as well, such as scorpions, spiders, etc. Insecticides are distinct from insect repellents, which repel but do not kill.

A cursorial organism is one that is adapted specifically to run. An animal can be considered cursorial if it has the ability to run fast (e.g. cheetah) or if it can keep a constant speed for a long distance (high endurance). "Cursorial" is often used to categorize a certain locomotor mode, which is helpful for biologists who examine behaviors of different animals and the way they move in their environment. Cursorial adaptations can be identified by morphological characteristics (e.g. loss of lateral digits as in ungulate species), physiological characteristics, maximum speed, and how often running is used in life. Much debate exists over how to define a cursorial animal specifically. The most accepted definitions include that a cursorial organism could be considered adapted to long-distance running at high speeds or has the ability to accelerate quickly over short distances. Among vertebrates, animals under 1 kg of mass are rarely considered cursorial, and cursorial behaviors and morphology are thought to only occur at relatively large body masses in mammals. A few mammals have been termed "micro-cursors" that are less than 1 kg in mass and have the ability to run faster than other small animals of similar sizes.

Some species of spiders are also considered cursorial, as they walk much of the day, looking for prey.

Nggam ([ŋgam]) is a type of divination found among many groups in western Cameroon. Among the best documented is its practice by the Mambila people of Cameroon and Nigeria, in which the actions of spiders or crabs are interpreted by the diviner. The form used by the neighbouring Yamba people was described by Gebauer, in 1964 based on experience in Mbem, going back to before 1939, and more recently by Hermann Gufler (1996 and 2003). Good documentation of Nggam has also been published for the Bekpak (Bafia) people by Dugast and Leiderer and for the Bamileke people by Pradeles de Latour. The crab form has been studied in north Cameroon by Walter van Beek (2013, 2015).

The comparative linguistics of spider divination in Cameroon was surveyed by Blench and Zeitlyn in 1989/1990.

The Cretaceous Terrestrial Revolution (abbreviated KTR), also known as the Angiosperm Terrestrial Revolution (ATR) by authors who consider it to have lasted into the Paleogene, describes the intense floral diversification of flowering plants (angiosperms) and the coevolution of pollinating insects (especially anthophilans and lepidopterans), as well as the subsequent faunal radiation of various frugivorous, nectarivorous and insectivorous terrestrial animals then at the lower food web levels such as mammals, avialans (early birds and close relatives), squamate reptiles (lizards and snakes), lissamphibians (especially frogs) and web-spinning spiders, during the Cretaceous period.

After the K-Pg extinction event devastated the Mesozoic terrestrial ecosystems and wiped out nearly all animals weighing more than 25 kg (55 lb), the survivors among these smaller animals that thrived during the KTR recovered first to reoccupy the ecological niches vacated by the extinction of non-avian dinosaurs and pterosaurs, and therefore became the dominant clades of the Cenozoic terrestrial faunas. Flowering plants also quickly became the mainstream florae during the Cenozoic, replacing the previously more prevalent gymnosperms and ferns.

In ethology, animal locomotion is any of a variety of methods that animals use to move from one place to another. Some modes of locomotion are (initially) self-propelled, e.g., running, swimming, jumping, flying, hopping, soaring and gliding. There are also many animal species that depend on their environment for transportation, a type of mobility called passive locomotion, e.g., sailing (some jellyfish), kiting (spiders), rolling (some beetles and spiders) or riding other animals (phoresis).

Animals move for a variety of reasons, such as to find food, a mate, a suitable microhabitat, or to escape predators. For many animals, the ability to move is essential for survival and, as a result, natural selection has shaped the locomotion methods and mechanisms used by moving organisms. For example, migratory animals that travel vast distances (such as the Arctic tern) typically have a locomotion mechanism that costs very little energy per unit distance, whereas non-migratory animals that must frequently move quickly to escape predators are likely to have energetically costly, but very fast, locomotion.

Structures built by non-human animals, often called animal architecture, are common in many species. Examples of animal structures include termite mounds, ant hills, wasp and beehives, burrow complexes, beaver dams, elaborate nests of birds, and webs of spiders.

Often, these structures incorporate sophisticated features such as temperature regulation, traps, bait, ventilation, special-purpose chambers and many other features. They may be created by individuals or complex societies of social animals with different forms carrying out specialized roles. These constructions may arise from complex building behaviour of animals such as in the case of night-time nests for chimpanzees, from inbuilt neural responses, which feature prominently in the construction of bird songs, or triggered by hormone release as in the case of domestic sows, or as emergent properties from simple instinctive responses and interactions, as exhibited by termites, or combinations of these. The process of building such structures may involve learning and communication, and in some cases, even aesthetics. Tool use may also be involved in building structures by animals.

The tapetum lucidum (Latin for 'bright tapestry, coverlet'; /təˈpiːtəm ˈluːsɪdəm/ tə-PEE-təm LOO-sih-dəm; pl.: tapeta lucida) is a layer of tissue in the eye of many vertebrates and some other animals. Lying immediately behind the retina, it is a retroreflector. It reflects visible light back through the retina, increasing the light available to the photoreceptors (although slightly blurring the image).

The tapetum lucidum contributes to the superior night vision of some animals. Many of these animals are nocturnal, especially carnivores, while others are deep-sea animals. Similar adaptations occur in some species of spiders. Haplorhine primates, including humans, are diurnal and lack a tapetum lucidum.

A piscivore (/ˈpɪsɪvɔːr/) is a carnivorous animal that primarily eats fish. Fish were the diet of early tetrapod evolution (via water-bound amphibians during the Devonian period); insectivory came next; then in time, the more terrestrially adapted reptiles and synapsids evolved herbivory.

Almost all predatory fish (most sharks, tuna, billfishes, pikes etc.) are obligated piscivores. Some non-piscine aquatic animals, such as whales, sea lions, and crocodilians, are not completely piscivorous; often also preying on invertebrates, marine mammals, waterbirds and even wading land animals in addition to fish, while others, such as the bulldog bat and gharial, are strictly dependent on fish for food. Some creatures, including cnidarians, octopuses, squid, cetaceans, spiders, grizzly bears, jaguars, wolves, snakes, turtles and sea gulls, may have fish as significant if not dominant portions of their diets. Humans can live on fish-based diets, as can their carnivorous domesticated pets such as dogs and cats.

Biting is an action involving a set of teeth closing down on an object. It is a common zoological behavior, being found in toothed animals such as mammals, reptiles, amphibians, fishes, and arthropods. Biting is also an action humans participate in, most commonly when chewing food. Myocytic contraction of the muscles of mastication is responsible for generating the force that initiates the preparatory jaw abduction (opening), then rapidly adducts (closes) the jaw and moves the top and bottom teeth towards each other, resulting in the forceful action of a bite. Biting is one of the main functions in the lives of larger organisms, providing them the ability to forage, hunt, eat, build, play, fight, protect, and much more. Biting may be a form of physical aggression due to predatory or territorial intentions. In animals, biting can also be a normal activity, being used for eating, scratching, carrying objects, preparing food for young, removing ectoparasites or irritating foreign objects, and social grooming. Humans can have the tendency to bite each other whether they are children or adults.

Bites often result in serious puncture wounds, avulsion injuries, fractures, hemorrhages, infections, envenomation, and death. In modern human societies, dog bites are the most common type of bite, with children being the most common victims and faces being the most common target. Some other species that may bite humans include urban animals such as feral cats, spiders, and snakes. Other common bites to humans are inflicted by hematophagous insects and arthropods, such as mosquitoes, fleas, lice, bedbugs, and ticks (whose "bites" are actually a form of stinging rather than true biting).