P. fimbriata are predatory, and they use several methods of predation. One is aggressive vibratory mimicry, in which P. fimbriata climb on to the web of their victim and use their legs and palps to pluck signals on the web. They imitate the signals of their intended victim's prey. When the victim comes close to P. fimbriata, they make their attack.
P. fimbriata are specialists at catching cursorial salticids. Most cursorial salticids don't build typical webs, but they spin orb-like nests out of silk. P. fimbriata make vibratory signals on the silk of the nest. When the salticid pokes its head out to investigate, they attack. This is called nest probing.
Another type of predation used by P. fimbriata is cryptic stalking. In this method, the hunter moves very slowly. If the salticid turns to face it, P. fimbriata pulls its palps back and out of the prey's view and freezes. In this position P. fimbriata resembles a piece of detritus. Eventually it approaches the prey from behind, and swoops in for the kill.
Other jumping spiders of the genus Portia exhibit aggressive mimicry, nest probing, or cryptic stalking. P. fimbriata is the only species that exhibits all three behaviors. P. fimbriata also displays species specific predation tactics. The jumping spider Euryattus (species unknown), is sympatric with P. fimbriata in the rainforests of Queensland, Australia, but is not known to exist with any other P. fimbriata population. Euryattus females do not build a nest, but suspend a rolled-up leaf by silk guylines from a rock ledge or tree trunk. Male Euryattus go down guylines onto the leaves and court by flexing legs and making the leaf rock back and forth. The female comes out of the nest to either mate or drive the male away. P. fimbriata mocks the behavior of the male, and when the female comes out of the nest, P. fimbriata attacks. Populations of P. fimbriata that do not live with Euryattus in nature do not drop down from guylines to attack Euryattus in this way.
Unlike other salticids, P. fimbriata are web building spiders. P. fimbriata use their webs not only as nests, but as a mode of predation. They build their webs near, and fastened to, the webs of another species, creating a single compound structure. It then is easy for a P. fimbriata to invade the neighboring web. The web of P. fimbriata is not sticky, but sometimes does catch insects. In this situation, P. fimbriata usually do not eat the insect, but wait for spiders from the a neighboring web to approach, and eat them instead. (Jackson 1985, Jackson 1998, Jackson 1992, Daiqin and Jackson 1997)