It is difficult to separate the ecology and behavior of spiders, except by viewpoint. The former is primarily involved with the interaction between populations of an organism and the environment in the long term, whereas the study of behavior is involved with the individual and its interaction with its conspecifics, potential prey items, enemies and habitat. The behavior of spiders is quite fascinating and is deeply enmeshed with evolutionary study of these creatures.
Prey capture, web construction (in web-builders), agonistic display and fighting, courtship and mating, egg-sac construction, maternal behavior, dispersal and defense are all potential aspects of a spider's repertoire of behavior. Several summaries have been published on spider behavior and a more complete picture can be found in these (Witt & Rovner 1982, Richman & Jackson 1992, Foelix 2010).
Prey capture behavior is found in all spiders and is the basis for the guild concept in their ecology. Individual capture methods become somewhat plastic when spiders with good eyesight are involved, especially the jumping spiders (Salticidae) (Jackson & Wilcox 1998). Other non-web building spiders are more stereotyped in their prey capture, with some crab spiders (family Thomisidae) simply waiting for an insect to land on a flower on which they have hidden themselves (see Fabre 1919 for a still fresh account of the European crab spider). Web-building spiders are fairly stereotyped in their prey capture behavior within their species, but the variety between species is quite staggering. They range from very complex orb webs to simple sheet webs, with a few having abandoned the web for a pheromone lure (Mastophora and several other araneid genera).
Web construction is a remarkable process, especially among the orb-weavers. These webs are the typical wheel-shaped, usually vertical, flat webs used often in the past as an inspiration for book decoration. The sticky (or woolly in the case of the cribellate Uloboridae) capture strands make up the spiral and the non-sticky silk forms the spokes of the web. It is on these non-sticky lines that the spider moves on the web, although they can also move on sticky silk. Three-clawed spiders use their third claw as a hook to grasp the silk lines. The web construction begins with a single line swung or floated by the spider between two objects (branches or other sturdy objects). The outside construction frame takes shape and some radii (spokes) are soon in place, meeting in the center of the frame. A spiral is laid down in the center and a quick outer temporary spiral (later torn down as the finer spiral is made). The spider then, using its own body as a measuring device (smaller spiders make finer webs) lays down the final spiral. A retreat is usually attached to one of the radii so that the spider can hide when not on the web. The construction of other web types is also interesting, but less well known (see Foelix 1996 for details on silk, webs, and web construction).
Agonistic displays and fighting, usually between males over mates or territory, is common among many spiders. These have been studied somewhat more in the Salticidae than in other families (Crane 1949, Richman 1982, Richman & Jackson 1992). Riechert (1978a, b, 1979, 1982) documented territorial competition in the funnel web spider, Agelenopsis aperta in New Mexico. There is, however, still much to learn about this subject, both in salticids and in other families.
Courtship and mating has been studied in a number of families, although the Araneidae, Lycosidae, and Salticidae have probably been more examined than other families (Richman 1982, Witt & Rovner 1982, Richman & Jackson 1992, Foelix 1996). Courtship in web-building spiders usually involves more vibrational signals. Pheromones become important in running spiders, such as lycosids(in which males will sometimes perform the entire courtship display if in contact with female silk), whereas sight and sound are the main senses involved in salticid display. Salticid courtship is a truly complicated affair, with posturing and display of brightly colored projections, hair fringes, faces and plume-like scales involved. Noises are often made that are inaudible to humans, but when amplified are quite startling. Females are occasionally active participants in the display, as in Habrocestum pulex, in which both spiders whirl around in a rapid spiral dance (Richman 1982).
Virtually all spiders practice egg sac construction, although some lack an actual sac, covering their eggs with a thin layer of silk (Richman & Whitcomb 1981). The eggs are produced from the female genital opening, often in a gelatinous mass; the mass is surrounded by heavy silk layers in most spiders (see Richman & Jackson 1992, Foelix 1996).
Maternal behavior in spiders is quite varied . The egg sac and the female are often enclosed in a sac of silk in some wondering spiders, such as salticids and heteropodids. In the giant crab spider, Olios giganteus, the outer sac is heavy and parchment-like. It is very difficult to break open and the female defends her eggs vigorously. Most web-building spiders suspend their egg sacs on their webs or on nearby branches. In wolf spiders (lycosids) the sac is carried on the spinnerets and in nursery web spiders (Pisauridae) and some giant crab spiders (e.g. Heteropoda) the egg sac is carried in the chelicerae. In most spiders the maternal behavior ends before or just after the emergence of the spiderlings, but in wolf spiders the newly emerged young climb onto the mother's back and remain there until the first molt out of the egg sac. They then disperse by ballooning.
Dispersal by spiders begins with the usual method, (see Bristowe 1939, Foelix 1996 for more detailed descriptions) except in some mygalomorphs, of ballooning as newly emerged spiderlings. These climb to the highest nearby object and spin out a strand of fine silk. When the silk line is caught by a breeze, the spider is air bourn and is often carried to great heights, especially if a weather system passes through at the time it is in the air. The silk is often seen in large amounts attached to trees, fences and other objects in the spring, or even late winter in the southern United States. Of course the spider has no control over where it lands and if it lands in an area that is unsuitable it will take to the air again. Some spiders, notably the smaller linyphiids, balloon throughout their lives.
Defense in spiders includes threat displays, biting, behaviors associated with mimicry (acting like an ant, or beetle, or freezing and looking like a lump of bark, flower part or bird dropping), or playing dead. Many spiders will defend themselves or their egg sacs vigorously. That is why it is dangerous to project body parts into a web of a black widow female if she has egg sacs. Threat displays, especially of the larger mygalomorphs, ctenids or sparassid spiders can be quite startling and undoubtedly will discourage some predators. Ant-like, beetle-like, and even velvet ant-like behaviors are apparently useful in convincing a potential predator that the spider can sting or is inedible. In some cases, velvet ant mimics for example, the bite of the spider may itself be very painful. Looking and behaving like a part of the landscape is useful both for defense and in prey capture (as in many thomisid crab spiders). A good summery of some of these behaviors can be found in Foelix (1996) and (for jumping spiders) Richman & Jackson (1992).