The long-jawed orb weavers (Tetragnathidae) were formerly included in the Araneidae; they are closely related, being part of the superfamily Araneoidea.
Generally, orb-weaving spiders are three-clawed builders of flat webs with sticky spiral capture silk.
Characteristically, the prey insect that blunders into the sticky lines is stunned by a quick bite, and then wrapped in silk.
Thus, the webs of orb-weavers are generally free of the accumulation of detritus common to other species, such as black widow spiders.
Members of the genera Mastophora in the Americas, Cladomelea in Africa, and Ordgarius in Australia produce sticky globules, which contain a pheromone analog.
Some scientists suggest that it could be through the spider's spatial learning on their environmental surroundings and the knowing of what will or will not work compared to natural behavioristic rules.
[7] The spiny orb-weaving spiders in the genera Gasteracantha and Micrathena look like plant seeds or thorns hanging in their orb-webs.
[9] The orb-web consists of a frame and supporting radii overlaid with a sticky capture spiral, and the silks used by orb-weaver spiders have exceptional mechanical properties to withstand the impact of flying prey.
Fossil evidence shows that the orb web was in existence at this time, which permitted a concurrent radiation of the spider predators along with their insect prey.
[12][13] The capacity of orb–webs to absorb the impact of flying prey led orbicularian spiders to become the dominant predators of aerial insects in many ecosystems.
[14] Insects and spiders have comparable rates of diversification, suggesting they co-radiated, and the peak of this radiation occurred 100 Mya, before the origin of angiosperms.
[15] Vollrath and Selden (2007) make the bold proposition that insect evolution was driven less by flowering plants than by spider predation – particularly through orb webs – as a major selective force.
[15] On the other hand some analyses have yielded estimates as high as 265 Mya, with a large number (including Dimitrov et al 2016) intermediate between the two.
Several fossils provide direct evidence that the three major orb-weaving families, namely the Araneidae, Tetragnathidae, and Uloboridae, had evolved by this time, about 140 Mya.
The morphological and behavioral evidence surrounding orb webs led to the disagreement over a single or a dual origin.
[19] While early molecular analysis provided more support for a monophyletic origin,[10][13][14] other evidence indicates that orb-weavers evolved earlier phylogenetically than previously thought, and were extinct at least three times during the Cretaceous.
[22] In the cannibalistic and polyandrous orb-web spider Argiope bruennichi, the much smaller males are attacked during their first copulation and are cannibalized in up to 80% of the cases.
These observations suggest that males can adaptively adjust their investment based on the degree of genetic relatedness of the female to avoid inbreeding depression.
[22] In one subfamily of Araneid that uses a mating thread, Gasteracanthinae, sexual cannibalism is apparently absent despite extreme size dimorphism.