Most spiders that we see in our day to day existence are Modern Spiders (Araenomorphae). They are the most common, the most obvious and those most often involved in bites, though rarely are these bites dangerous.
Crab spider (Amyciaea bimaculata).
Most Modern spiders explore the many uses of silk, from wrapping prey, to protecting their eggs and making webs. Many young pull out long lines of silk that allow them to fly on the wind. Spiders also use their wind-blown silk to start the main spans of the webs.
Modern spiders include:
These spiders have fangs that pinch together and have only 1 pair of lungs.
Generally, identification of Modern spiders at least to family, often to genus and sometimes to species is possible without harming the spider. Often, good photographs alone will suffice. But the most useful information in recognising a spider is its behaviour. Often, recently studied Australian spider families in Australia are the most accurately identified.
Males, whose body has often shrunk strongly from the plump state seen previously, and whose behaviour is geared strictly to safely finding the female, are generally harder to match to their female.
Most Modern spiders live only for 1-2 years, although Daddy-long-legs and some of their smaller relatives live for 5-7 years.
Old Huntsman spider skin left hanging by a thread after a moult.
Most are very seasonal. They emerge from eggs in late May and struggle through the cooler, drier months as young. In the spring, with rain and increasing warmth, growing insects provide the spiders with food to grow. By December, most spiders are adult. Males are searching for females and growth and mating continues usually until about April when the eggs are "laid".
Once mature, the male spider has a relatively short life (maximally 3–6 months). His purpose is simply to find a female and mate. As an adult, the male transforms into a long-legged, often spiny and less ornate spider designed for actively searching for the female. Guided partly by the air-borne scent (pheromone) of the female and possibly her silk, he wanders at night searching across trees and bushes and is often blown through the air by the wind.
Once the male finds a female mating takes place in the web. The mating structures of male and female spiders are often quite complex and a unique shape for each species. Mating in spiders is a potentially dangerous event and often fatal for the males whose sole purpose, once adult, is to mate. Some, like the Redback Spider (Latrodectus hasseltii), die during or just after the mating, often eaten by the female; others escape but die naturally soon after. Female araneomorphs reach maturity, mate, construct egg sacs and die.
Some days, or up to a week after mating, the female makes the egg sac into which she places the eggs and during that process, the eggs are made fertile. The egg sac is usually somewhere up high but, remarkably, the Golden Orb Weaver (Nephila pilipes) buries her eggs.
Wolf Spiders are protective and carry their young on their back for several days and some Huntsman spiders escort their young away from their territory but most spiders do not practice any maternal care and abandon their eggs once they are laid safely hidden.
After several weeks, the spiderlings, now dark in colour and having moulted once in the egg sac, chew a hole in the egg sac and emerge to moult once or twice before drifting off on the wind to hunt for themselves.
These spiders explore many different and remarkable hunting behaviours.
Black-ant-mimicking Jumping spider.
Monkey-faced Jumping Spider.
Some sit and wait in burrows in the ground or in the web, some look or smell just like ants or weevils, some wander freely at night (mostly), while others rely on excellent camouflage to conceal their presence. Some behave like sticks or have bodies as hard as rock and, as David, take on Goliath-like spiders.
The two most diverse groups are spiders that use their webs to hunt and the Jumping Spiders.
Webs that spiders build to hunt are remarkably diverse but many are based around a circle of silk, using several different kinds of silk. In some, the circle is adorned by intricate shapes. In others, the circle is modified strongly into a sheet or dome as in Money spiders (Linyphiidae) or Dome web spiders (Cyrtophora moluccensis).
Some build large sticky webs which may be yellow as an additional attraction. In some, the web smells like a female moth and attracts the male, in others the silk smells like rotting fruit or faeces and attracts flies.
Jumping spiders, on the other hand, use little web but have developed telephoto eyesight second only to the great eagles. With this excellent vision and ability to jump many times their body length, many brightly coloured and amazing species of Jumping spiders have evolved.
Probably one of the most common predators of spiders is spiders themselves. Cannibalism is common. As the young develop, brother will eat brother and older spider will eat younger.
Web building spiders are often taken by birds and ground hunting ones by lizards.
Large Spider Wasps (Pompilidae) are diverse both in the size range of the spiders that they hunt and the range of families. Often, the wasp, needing its prey compact to provision the nest for its young or even simply to fly with the spider, will cut the spiders' legs off.
White-tailed spiders (Lampona species, family Lamponidae), special flies (Acroceridae), threadworms and Gordian worms and even fungi which infect the spiders are amongst some of the more insidious causes of spider death.