A bolas spider builds no orb. The adult female hangs beneath a horizontal support line, holds a short thread ending in a droplet of glue, and waits with a foreleg raised. When a moth arrives she swings the line at it; a hit sticks fast, and the spider hauls the moth in.
The attraction is chemical. The spider emits volatiles that mimic the sex pheromone blends released by female moths of particular species, so the males that approach are answering what they take to be a mate. Some species alter the blend through the night, matching moth species that fly early and those that fly late, which widens the range of prey a single individual can draw.
Juveniles hunt differently. Too small to swing a bolas effectively, they capture flies and other small insects directly with their front legs, and some are reported to attract them chemically as well.